I thought the problem was solved because it stopped happening for awhile. Although recently this problem has started again and the new solution I have is to remove the sim card and reinsert it. This is my only solution but seems to resolve the problem faster than a restart.
This is also reported on T-Mobile forums:
When I contacted Samsung, they insisted it was a problem with my device, even though everyone I know with a T-Mobile version suffers from this issue. Going forward, I'm jumping off the Samsung bandwagon, as their support are low level script readers and no one is willing to actually raise a bug with the product team.
Here are my findings:
This issue began with the September 4x4 MIMO firmware update, and wifi calling seems to have something to do with it, where wifi calling preference selection is not being honored. Generally, you see the issue manifest itself when you pass through an area of no signal, then the device fails to reestablish network connectivity once you come back into an area with signal. When this occurs, your device says 'no service', however if you go to the dialer screen and type *#0011# you will see the device is in fact connected to the T-Mobile network, but it just isn't using it. This is the indicator that led me to test wifi calling, as this is how the device hands off between IMS over wifi and IMS over LTE.
When this occurs, you have 2 options.
Option 1: Just reboot - this, in most cases, is faster.
Option 2: if *#0011# indicates "Serving PLMN(310-260)", then you are connected, and following these steps will get you back up and going without a reboot.
1. Go into your wifi calling settings.
2. Ensure wifi calling toggle is on
3. Start with cellular preferred, wait 3 seconds, then select Never use cellular, wait 3 seconds, then select wifi preferred, wait 3 seconds, select cellular preferred, wait 3 seconds.
4. Turn off wifi calling toggle and wait 5 seconds then toggle wifi calling back to on.
5. Repeat step 3.
After this process, when selecting wifi calling preferred (as long as wifi is off with wifi calling on, per instructions) signal will come back after the 3 second wait, then I always end with cellular preferred.
Phew, that was a mouth full!
Hope this helps someone. I do this all the time, but my wife can't seem to nail down the process, so she just reboots every day after exiting her elevator at work.
I'm not 100% certain, but I believe if you turn wifi calling off, reboot a few times, and never turn it on again, the issue is gone for good. If you need wifi calling and you have to enable it, be sure to turn it back off and reboot twice (about 15 min apart) to keep the issue at bay.
P.s. please excuse any typographical errors, as I am typing this from my phone.
One thing to note:
Where I said this, in my previous post:
"I'm not 100% certain, but I believe if you turn wifi calling off, reboot a few times, and never turn it on again, the issue is gone for good. If you need wifi calling and you have to enable it, be sure to turn it back off and reboot twice (about 15 min apart) to keep the issue at bay."
This removes the issue from my phone, but not my wife’s, so I don’t know what’s going on there.
With that said, Yesterday, I needed Wi-Fi calling, turned it on, and as soon as I received signal again, I had no data once Wi-Fi was off. Data was enabled, but it did not work. *#0011# showed I was not connected to LTE but rather the HSPA network. I toggled airplane mode, which resulted in no signal at all, and *#0011# showed i was now connected to the LTE network. Upon toggling Wi-Fi calling settings, my phone promptly reconnected to the cellular network.
Hope it helps someone else, until Samsung and T-Mobile decide to acknowledge the issue and resolve.
Really sorry there's been a small response in reference to this. Just wondering if anyone has talked specifically with T-Mobile, and if so, what were you told exactly? Also, has anyone tried to setup an evaluation with our Phone Support Team, to possibly see if perhaps there's an underlying hardware problem acting up with your specific device?
I did and was told to try turning Voice Over LTE off. Didn't Work For Me. Called Samsung And they stated that they can't detect anything. Hopefully new Nougat update fixes this!
Please do update back if disabling WiFi Calling works out for you @usere2tz4B1vH8.
I'll see what I can find out as well on my end about this. Seems like for whatever reason, there's just a problem with that network connection establishing once going out, even if displayed accurately.