Solved! Go to Solution.
BTW, I have flashed T-Mobile firmware on my Note20 Ultra from time to time but currently on unlocked firmware. AT&T and Verizon are different though. Unless you buy their branded phones, no successive updates even if you flashed it with their firmware.
Not true. I always have unlocked Samsung phone with T-Mobile. I have wi-fi calling, wifi connection at the airport is t-mobile wifi available, and also wifi calling every time when connecting to wifi.
I have an unlocked s22 plus and when I took it to Verizon I couldn't use the spam calling app
So carrier exclusive apps might be the only problem
Also you might not get the UWB 5G speeds