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Wifi Calling not working on Non-T-Mobile Galaxy S9?


    Hello all,


    I'm hoping that someone might have some insight, know a fix, etc.


    For the last few years I've been stuck on a T-Mobile branded Galaxy S5 and Wifi calling and advanced texting features work fine. Now I've received a AT&T Branded Galaxy S9 - Model SM-G960U of which I obtained a Samsung unlock code for it. I had T-Mobile change my Sim card and update the my account yesterday with the new IMEI, etc. but WiFi Calling will not enable although it's built into the phone features.


    When I put an active AT&T Sim card into the phone, WiFi calling works.


    Has anyone else tried using a Non-T-Mobile S9 yet with their T-Mobile service and if yes, is your WiFi calling working?


    Anyone know if I need to find a T-Mobile Firmware ROM for the S9 and flash it get the features to work?


    *I do know that since the phone is not T-Mobile branded, T-Mobile can't be much help*


    Thanks in advance for any help with this.

      All replies

      • theartiszan

        This is due to it being a different carrier phone and the software is configured to work with att WiFi calling and not a general or dynamic sense. There really isn't much TMobile can do as you pointed out. You can attempt to put TMobile firmware on it. If it runs that should fix the problem. Just know there are always risks in flashing different firmware to your device. It won't be as simple as just getting the TMobile file. I would suggest looking up xda and see in anyone has done this yet. I believe people were successful with the s8 and a modified version of Odin.

        1 of 1 people found this helpful
        • dragon1562

          I just wanted to add the theartiszan answer is correct. If you were to somehow flash the T-mobile firmware on you would be set but it may be easier just to get a T-mobile device.

          • dragon1562

            You could also get a booster for your home if that is where the wifi calling was needed. Just figured I give another possible solution.

            • jrockz

              Thanks for the replies. I would get a T-Mobile device but these new phones are too expensive and I received my S9 at no cost. Guess I'll have to wait for Sammobile or XDA to hopefully capture and post the TMO rom's.


              I've had the boosters before and they did not work well in my house. I only had the 4G models. I returned them

                • whyhellothere

                  Im in the same boat as you...



                  I have a Verizon s9, g960u with a tmobile service.


                  Outright, I didnt have to do anything to the phone, as these are SIM unlocked, (difference in carrier firmware lock and sim unlocked)




                  here is your first reference:

                  G960U Firmware Links Here | Samsung Galaxy S9

                  here is your second, where the TMOBILE firmware is:




                  it wont trip KNOX and you dont have to have your bootloader unlocked.




                  However this is risky.


                  once you flash this successfully, WIFI CALLING WORKS and VIDEO CALLING as well as Visual Voicemail


                  let us know what the end result is

                  1 of 1 people found this helpful
                    • jrockz

                      Thank you for the info. Since you mentioned that you are\were in the same boat, did you happen to successfully flash you phone? Based on your info about once it's flashed, the WiFi Calling, etc. will work.


                      If you did successfully flash yours, anything special that you did? Which version of Odin, etc.


                      Thanks again.

                        • whyhellothere

                          NP at all!


                          So WIFI CALLING, VIDEO CALLING works, visual voicemail works.


                          the only thing I cannot verify is if the TMO firmware enables the sleeping Network bands on my Verizon S9.



                          from what I read, as long as it is ODIN 3.1+


                          However you can go here: this talks about it and someone modded their ODIN:

                          [HOW TO] Flash U1 firmware to U device | Samsung Galaxy S9


                          the actual modded odin is here:

                          Modded Odin v3.13.1 - Google Drive


                          1. Disable all locks to the phone including samsung and google (remove these accounts)

                          2. Enable debugging, -> developer mode

                          3. from the ODIN zip, extract and run ADB (assuming you got all drivers)

                          4. Fill all the nessesary fields ODIN is asking for (AP, BL, CP, CSC) the modded odin will have a USERDATA field - this is where all tmobile bloatware is



                          you can also refer to this:


                          How to Carrier Switch and Firmware Flash the Galaxy S8 Snapdragon -

                          but this is for the S8, similar steps.


                          Good Luck!

                            • jrockz

                              Well, I tried a few times and it did not work for me. I followed the steps, Odin says that it flashed the firmware, but upn auto reboot, it still has the AT&T firmware.


                              I tried this process with and without the User Data file. I even tried a factory wipe after the phone rebooted. Boot-up sound and logo is still AT&t, the only small thing that I did find that the flash did was add a TMO Visual Voice Mail icon on the screen, but nothing else.

                                • whyhellothere



                                  I keep getting errors on the TMobile forum when I sign in, I'll try again




                                  But on your system about:


                                  Does it show g960u1 ?



                                  I've heard some people had to factory reset.








                                  Also on this firmware you can do this: optional

                                  Reboot phone, using the Samsung dialer,

                                  Dial: *#2263#

                                  And select all lte bands.

                                    • jrockz

                                      The model in about shows: SM-G960U (this is a AT&T model) not a Samsung Direct Model.


                                      I did verify that all LTE bands are enabled and I've also tried the factory reset after flashing.


                                      Maybe this model can not be flashed since it's not a Samsung Direct Model with the optional OEM Boot Locker Enable\Disable option.


                                      I have a T-Mobile Firmware branded GS7 and in developer options, there is the option to enable the OEM bootloader unlock. (if that makes sense)


                                      Thanks again for your time trying to assist me. It's greatly appreciated.

                                        • whyhellothere





                                          From the earlier posts I put up,

                                          I referred to the U1 firmware and the TMobile firmware.



                                          I don't think it's flashing properly, Odin says success right?



                                          Keep in mind that the North Amera Sim Unlocked version from Samsung's

                                          bootloader is also locked. You can only unlock bootloader's from the

                                          international versions.

                                          The one from Samsung is the g960u1




                                          So mine is not directly from Samsung, but from Verizon, I flashed my u to

                                          the U1 and as well as the TMobile version.



                                          So you allowed us debugger, then you connected the phone, you ran adb from

                                          command prompt. Reboot to bootloader, then flash from odin.




                                          What files are you flashing btw

                                          • whyhellothere



                                            try this,


                                            download the firmware here:




                                            this is the U1 from samsung, this is just compressed, but itll unpack to

                                            about 3.9-4.1GB





                                            then grab this:


                                            unpack to desktop,


                                            then you are going to run CMD, and CD to the PLATFORM tools directory (you

                                            unpacked to desktop)








                                            then run the MODDED odin which you downloaded, and place accordingly.


                                            This should flash for you.


                                            Remember the U in G960 means unlocked. U1 is just the unbranded version

                                            from samsung.


                                            Your phone from ATT is unlocked, but carrier firmware does lock certain

                                            things to make it feel like the phone is locked.




                                            I tried the tmo firmware, and got sick of it so I went to the U1, i think

                                            there is something being missed during the flash steps.


                                            let me know!

                                              • tmo_chris

                                                Some good info here but in full disclosure, this will void the warranty of the device and T-Mobile does not support this in any fashion.

                                                1 of 1 people found this helpful
                                                • jrockz

                                                  Thanks. I am going to try this today.

                                                  • jrockz

                                                    Sorry, but I'm a little lost on this part of your instructions.


                                                    "then you are going to run CMD, and CD to the PLATFORM tools directory (you

                                                    unpacked to desktop)"

                                                    • whyhellothere


                                                      download the firmware here:  THIS IS NOT TMOBILE version, it is what Im using, I like it




                                                      this is the U1 from samsung, this is just compressed, but itll unpack to

                                                      about 3.9-4.1GB




                                                      Okay, so download this, place this on your desktop, and create a new folder on desktop called "ADB"

                                                      then unzip all files from here:




                                                      Then from windows, run command prompt

                                                      then once it launches, type this in:

                                                      cd C:\Users\XXX\Desktop\ADB


                                                      (XXX is your username)


                                                      3. allow usb debugging from developer mode, phone - software information - tap build number 7 times to unlock dev mode, then enable usb debug from dev options



                                                      4. plug in to a non charging USB port. once you plug in you should now get a pop up on your phone to allow the connection from your computer


                                                      5. go back to CMD prompt, and type: adb devices

                                                      and verify that it can see your phone.


                                                      6. run the modded odin, place all of the files to its category, and ODIN should say SUCCESS.


                                                      from there, your phone will boot, this time only showing SAMSUNG.


                                                      once booted, from samsung dialer dial: *#2263# select all LTE bands, reboot.



                                                      then the first thing you should do is run, SAMSUNG dialer, go to settings:

                                                      WIFI CALLING should be below: "RINGTONES and KEYPAD Tones"







                                                      so as you can see, theres sequences to these things. im sure you did all of that, but try this step.



                                                      i dont think i can leave my information here so you can DM me if you need assistance

                                                      1 of 1 people found this helpful
                                                        • whyhellothere

                                                          I forgot to add,


                                                          after Step 5, go back to command prompt and run:

                                                          adb reboot bootloader

                                                          while the phone is connected, and should bring the phone to download mode

                                                          1 of 1 people found this helpful
                                                          • jrockz

                                                            Thanks. yeah, I don't need to the TMO version really as long as I can get the WiFi Calling to work. I don't use Visual VM, but it would be nice if it works.

                                                            • jrockz

                                                              whyhellothere IT WORKED! I followed your new instructions, I was able to flash successfully. I then decided to flash the TMO ROM and it's also working!


                                                              Thank you! Thank You! Thank You!


                                                              Now using your same instructions, I should be able to flash my co-workers AT&T S8 to TMO. I assume I would just follow the same instructions you provided and I just need to find the TMO S8 ROM and first make the S8 into a U1?

                                                              • jrockz

                                                                whyhellothere , Hell again,



                                                                So it seems that after flashing the TMO Rom, it locked the bootloader. I attempted to go back to the Samsung U1 version but odin fails on the bootloader.


                                                                Any ideas? It seems like you were able to flip flop on your "U"

                                                                  • jrockz

                                                                    whyhellothere , does it matter that I used the same modded odin prog. to flash the TMO rom?

                                                                      • whyhellothere

                                                                        Hey Jrockz



                                                                        On ODIN it fails when you flash the bootloader right?




                                                                        can you tell me the steps you took, and the sequence?



                                                                        You went from ATT to U1, then U1 to Tmobile, then Tmobile back to U1 or ATT?






                                                                        The modded ODIN, allows you to flash the U1 firmware, (technically 960u is not supposed to be flashable with u1, thus the modded md5 odin)


                                                                        You may need to get another dev to mod ODIN for Tmobile's purpose.




                                                                        ALSO, the TMO Firmware maybe a NEWER release from the U1 version, which makes sense if you cant flash it.

                                                                        What you can do is search around for a modded ODIN, or wait for the new U1 firmware...






                                                                        try to hit up XDA and see if there is a newer or different modded odin.




                                                                        Just out of curiosity, did video calling work for you on tmobile firmware?

                                                                          • jrockz

                                                                            Thanks for the reply.


                                                                            So yeah, for trying to flash back to U1, I followed the exact same steps you gave me for flashing. It does fail at the bootloader and currently I am in agreement that I think that the issue may be with the TMO Firmware being newer and/or a newer security patch level than the U1 firmware of which would make it not "down gradable"


                                                                            I tested video calling yesterday and it does work with the TMO firmware.

                                                                            • amonra

                                                                              Hi all,


                                                                              i am being told by a Samsung rep that the hardware that enables WiFi calling is missing from the unlocked phones. This sounds odd. Has anyone heard or confirmed this?


                                                                              Moinuddin Syed (Samsung E-Commerce)

                                                                              Aug 1, 03:00 EDT

                                                                              The unlocked version will not have the option to turn on Wi-Fi calling as the hardware which supports the feature is not available in Unlocked version.


                                                                              1) is this really true??

                                                                              2). I don’t yet have an S9 (I did, but returned it for this exact issue). i still would love to have an S9, but WiFi calling is critical for me. What is my best option: a) buy unlocked (if yes, which variant) and get) and get WiFi calling to work - this is my preferred route if viable - or b) Buy from T-Mobile. In this case how do I get rid of the annoying startup jingle (definitely need that gone) and if possible the T-Mobile logo?


                                                                              thanks all! This would be my first venture out of the Apple world, but so far it’s proving to be unnecessarily complicated

                                                                                • amonra

                                                                                  On the third try, I think I figured out the WiFi calling issue on unlocked devices (Galaxy S9).  The key is to have the T-Mobile SIM card in the device before starting the setup for the first time. Doing this, the first popup I got said that the device will be updated with carroer specific settings. Then i went through the setup, and WiFi calling was there in the Phone app -> settings.

                                                                                  On another device o went through the setup first and then popped in the Tmobile sim, and the same window about carrier settings never presented itself.

                                                                          • muntherkubba

                                                                            Hi whyhellothere,


                                                                            I am new to all this. I just purchased the Unlocked Galaxy S9+ International Version SM-G965F/DS. I am using with T-Mobile and discovered that WiFi calling and a few other features don't work. As you know, the processor on this version is the Exynos and not Qualcomm. Does the procedure you listed work on this S9+ phone version? Does the phone have to be rooted in order to perform your instructions?


                                                                            Thank you indeed,