Constantly told SIM card has been removed on Google Fi

    I have a Pixel with a Google Fi SIM as a secondary phone. I'd like to use DIGITS to access my T-Mobile messaging from my Pixel, as I'm occasionally out of range of T-Mobile towers. However, DIGITS constantly logs me out, telling me that my SIM has changed. This is probably because Google Fi works by connecting to one of three cell providers depending on the signal strength of each at any given time. I assume that whenever it switches providers, DIGITS detects it as a SIM change.


    Phone: Google Pixel

    OS: Android 7.1.1, stock

    Mode: One number, multiple devices, non-T-Mobile carrier

    Secondary carrier: Google Fi (Google Voice on top of T-Mobile, Sprint, and US Mobility)

      All replies


        Exact message: "SIM change detected" "SIM card inserted, you will be signed out."

        • tmo_mike_c

          Hmm, this is very interesting. When you opted for one number with multiple devices, were you sent another SIM card by T-Mobile for your Google phone? Is the Pixel phone the one with the primary SIM with the phone number you want to duplicate, or is this the phone you want the duplicate line with?


              No, I wasn't sent another SIM card because I chose to use the number on a phone with another carrier.  Here's my configuration:

              • Samsung Galaxy S6, T-Mobile SIM
              • Google Pixel, Google Fi SIM

              My primary number is the T-Mobile number.  I want to be able to send and receive SMS messages on my Google Pixel using the Google Fi SIM.  This is a supported configuration according to the DIGITS beta I signed up for (use T-Mobile number on a phone with another carrier's SIM, vs. on a phone with another T-Mobile SIM).  I'm fairly certain the only reason it doesn't work is because Google Fi switches carriers frequently--the "SIM change detected" messages correlate with the carrier changes.


              Remember, this is the DIGITS beta; it's not the pre-existing single-line-multiple-device option, if there was one previously.


              As a security note, it's possible to cancel the logout process if I open the notification and exit the app at exactly the right moment, and I'll continue to stay logged in on the new carrier.  However, the timing is tricky if I do it manually, so it's not a viable workaround; 80% of the time I end up logged out.  It'd be easy enough to automate for a 100% success rate, though.  Also, if I avoid opening the logout notification, I'll continue to receive incoming messages and calls as notifications, as I'll never be logged out.

                • tmo_tim_b

                  Hello Paul -


                  We definitely appreciate the information and your participation in the beta. I'd like to get this reported. I was wondering if since our last contact if you've discovered any other information regarding this that could be useful? I agree from what you've said so far it seems like that's how it works with Google Fi. Does Google Fi provide a virtual SIM card update each time it moves to another carrier? That would make the most sense to me. Most phones don't change carriers like that, so a SIM card change wouldn't be an issue for most devices/services.


                  Thank you.

              • tmo_evan

                Unfortunately we're not able to support Google Fi using "calling via minutes".  The main issue is that the Google Fi service is constantly switching between different networks (primarily T-Mobile and Sprint) and thus the phone is actually swapping in 2 different SIM cards with 2 different underlying numbers.  Since this is functionality that is "masked" from some applications that rely on making call and DIGITS is trying to use the network natively, this translation can't be supported.


                If you want to use DIGITS on the Google Fi network, we recommend going into App Settings and switch to "Data only" rather than "using Minutes" since this will ignore any underlying SIM card changes across networks.


                    tmo_evan It seems I've actually been on the "Use data only" setting.  I certainly didn't set that deliberately--in fact, I remember ensuring that it was set to both "Use minutes and data".  This could be a result of exiting the app before allowing it to log out if it temporarily switches to "Use data only" as soon as it detects the SIM change.


                    Although the underlying numbers are different for each network (I assume, since I don't know how it would work otherwise), there's an overarching Google Voice number that connects all of them, and that's the number typically reported to apps.  The idea of having a dominant VoIP number isn't unique to Google Fi.  The SIM changes aren't masked (the app is definitely picking up on them), but I believe the underlying numbers are.  However, those aren't really the numbers that DIGITS--or anything else--should be routing to.


                    I believe the PUK was included with the SIM card, so I might poke around in it to see exactly how it works if I get a chance.  That could certainly explain why I'm getting four times as much spam on Google Fi as I'd normally expect--four times as many recycled numbers.


                    Slightly off-topic: It's worth noting that Google Fi actually supports a third network, U.S. Cellular (which I've erroneously been calling US Mobility).  That's actually the reason I got it: much of northern New Hampshire is no longer covered by T-Mobile and Sprint.  This wasn't a problem until sometime in the past year or so.  I only see towers from U.S. Cellular and AT&T around there; AT&T sort of lets me roam with them, but data seems to be blocked, even when I'm right next to a tower.  That location will be the real test to see whether this whole setup is working, but I probably won't be there for a few months at least.

                  • tmo_tim_b



                    I just wanted to check in with you. Based on the information provided by Evan and what you've discovered on your own, do you have any further questions regarding this? We definitely appreciate the information you have provided!


                    Thank you.

                    • magenta1670536

                      Same problem here on Iphone 6s.

                      I began noticing this about 1 month ago, but since I do not use my Digits line that often i really didnt care. WEll, I do now have to use it more frequently and I am missing calls and messages because of this. EVERY time I want to open the app it tells me it will sign out because I am missing the SIM card. It is frustrating.


                      Also, the digits line I got belong to someone else and I keep getting weird messages and calls for that other person. What can I do?