I have seen data work on T-mobile with B2, B4, and B12 (and assume voice would work too). B41 has never worked. When it is on B41, I need to turn on and off airplane mode to get it to pick another band temporarily.
I did get a new SIM, in case that would help with band 41 (which used to be Sprint, and is also a shared band between LTE and 5G). It still doesn't work with band 41.
Most places, I am on band 4. Unfortunately, sometimes, even if band 4 is a stronger signal, T-Mobile will switch to a weaker band 41 signal.
Because we have a Qualcomm modem, the apps for locking/blo