Can't make voice calls in certain areas, good 4G signal


    In Tionesta, PA I have good 4G signal but voice calls fail, by fail I mean that if a call is initiated the dialer just doesn't connect and the call is terminated, in other areas I don't have issues making or receiving calls. I'm on the $30 prepaid plan using an unlocked Blu R1 HD (Android 6.0) with the most recent updates so Band 12 and VoLTE are enabled, and "Enhanced 4G LTE Mode" is enabled in settings. In the problematic area there is a notification "Data Connection Only" and the network name doesn't list "T-Mobile" instead it says "Emergency Calls Only".


    I suspect that VoLTE isn't working correctly on my phone and that this area is only serviced by LTE Band 12 with no 2G or 3G to fall back on. According to LTE Discovery the Band I'm connected to is Band 12. The data connection works fine and my connection speed is ample 20.1 Mb UL / 5.8 Mb DL according to Speedtest. I haven't changed any phone settings and phone is not rooted. The T-Mobile US LTE APN settings look as suggested as far as I can tell, the only questionable settings are MVNO type = GID and MVNO value = 544d. Also there is a second APN T-Mobile US IMS that I'm unsure of the correct values. Is there something I'm missing that could cause an LTE only connection without voice or any suggestions of how to resolve the issue. I'm currently testing T-Mobile with the objective of subscribing to the One plan if the network is ample enough in my area so The Blu R1 HD wouldn't be my longterm phone.

      All replies

      • tmo_mike_c

        I did check that general area and I'm no seeing any tower issues. For the most part, the coverage looks pretty good especially outdoors. There are some areas, however, that the coverage does taper off a bit depending on exactly where you are. Are these specific address where you notice you're having trouble?Are they basically the same areas, or have the problem locations changed? You'd want to make sure you have solid signal while in those areas and you could even try a manual network selection to see if your phone can reconnect. Please let us know if you need more help.

          • callmeajs

            Thank you. Coverage is defiantly good, I can make VOIP calls using Google Hangouts via LTE in this area. As far as I can tell there is no 2G/3G in this area because if I manually select a network mode other than LTE I get a No Service indication. I currently have an engineering ticket in progress regarding the lack of VoLTE.

              • tmo_mike_c

                I checked my internal coverage map again, and I don't see any info about 2G or 3G changing. I feel like putting in a ticket with engineering to help with the LTE is a good thing. We'll need to wait on a reply from them for the status of the coverage in that area.

                1 of 1 people found this helpful
                  • davewise

                    I'm new here, and I have a similar problem.  Should I start a new thread?


                    Hillsboro, Oregon 97123

                    LG Leon LTE H345

                    Straight Talk MVNO


                    Recently, near home, the phone has begun to fail on voice calls - "Mobile network not available"

                    - even though there's plenty of signal.   (Note: T-Mobile hasn't enabled VoLTE around here yet.

                    And enabling or disabling VoLTE in the phone has no perceptible effect.)


                    It occurs 100% of the time when the phone is connected to one particular

                    tower on LTE Band 2.  (I haven't discovered B2 anyplace else in town, which makes me wonder if it's a test.)

                    For the curious, it's GCI 01810A0C PCI 141 TAC 13800.


                    With B4 or B12 it's 100% fine, it falls back to W-CDMA or HSPA+ during the call, but not B2.

                    And on B2, SignalCheck Pro says "Telephone calls are unavailable".  What does this mean

                    at the bits and bytes level?  Why would fallback work on some bands but not others?

                    (By the way, my home B4/B12 signals come from the same PCI - 141 - but different TAC - 13602.  I'm suspicious.  Am I catching a Stingray?)


                    Where can I learn more?  Is this a problem in the phone's configuration,

                    in the phone's firmware or hardware, or in the base station?

                    As a workaround, is there a way (perhaps via the 277634#*# engineering menu)

                    to disable Band 2 without disabling LTE entirely?



                    Dave Wise

                      • davewise

                        The same evening, the symptom went away.  The phone still connects to B2, but it immediately switches to B4 or B12.  Did they push something into the phone, or change the tower programming?

                          • tmo_chris

                            Hey davewise,



                            This is an interesting issue you have here. Typically, we would open up an engineering request for issues with calls failing on LTE but I noticed you said you had Straight Talk, is that correct? If so, you may need to reach out to their tech support group to see if they are able to open up a request with their engineers.

                              • davewise

                                This particular phone is using T-Mobile's network, and ST's first-line tech support wasn't useful.  They read script at me until I went away.


                                The symptom is still in remission.  The phone idles on LTE most of the time.  Every time it reconnects after CSFB, it connects on B2, then immediately switches to B4 or B12, regardless of signal strength.  Care to speculate on what's going on?  And on what changed?  Is B2 LTE a new thing in my area?  (Hillsboro, Oregon.  PCI is 141.  Where is that antenna?)




                                  • tmo_chris

                                    So T-Mobile does have LTE 700A in Hillsboro. I can't really speculate what specifically is going on in your situation as the agreement Straight Talk has with us may have varying degrees of what is supported and what is not supported. I am sorry for being so vague but the truth is I really don't know and I don't want to give you inaccurate information

                                      • davewise

                                        Yes, I see (and use) Bands 12 and 4.  (Also see B2 but as I said, the phone no longer stays on it.  It's as if B2 has some attribute or lacks some capability that makes the phone reject it.  Like perhaps CSFB?  How does the base station send this?  Where is it in the ETSI Technical Specs?)


                                        I don't know any particulars of ST's agreement with T-Mo, but I didn't expect it to go that deep on the technical end.  I just visualized them "buying minutes", since I don't have enough facts and detail to form any picture clearer than that.

                                          • tmo_chris

                                            I wish I had more info for you davewise I would recommend that you reach out to your provider again and see if there are able to open a support ticket to see what is causing this. If there is some sort of agreement restriction, their engineering team will let them know and they will relay that information to you.

                                            1 of 1 people found this helpful
                                            • davewise

                                              A new development.  Yesterday (March 29), the phone was "Mobile network not available" again, all day and evening.  SignalCheck Pro reported "telephone calls unavailable" on all LTE bands (2, 4, 12), where previously this was only the case on 2, and LTE Discovery said "Potential eCSFB issue detected".  This morning (March 30) it's as previous, connecting to 2 then jumping to 4 or 12 where voice calls go through.

                            • dragon1562

                              Is there anyone else that you know that has T-mobile. Could be a phone issue .