I already had them unlock my OnePlus 8 and pixel 3a xl about three months apart before my EIP is up.Try asking tmobile, you might get lucky and have a person perform a permanent sim unlock for you.
That's interesting, haven't heard of that before. I had success in the tmobile app and just told them I would like to root my phone to use my "tool" (viper4android/adaway) and that I have to switch between phones to have access to my tools.I already had them unlock my OnePlus 8 and pixel 3a xl about three months apart before my EIP is up.
They said that there is a maximum of 2 device unlocks before the EIP is fully paid off.
Whether or not that's true is anyone's guess.
I used T-Mobile T-force support team on Facebook to have the others unlocked.