Most here w/relatively new T-Mobile devices have seen this app: https://play.google.com/store/apps/details?id=com.tmobile.simlock&hl=en Just a BTW,in case you are interested in (SIM) unlocking your device: You will need to be on stock firmware in order for this to work. I found this out 1st hand,& had to revert back to stock on my HTC 10. For all you HTC users who root/ROM,I didn't have to revert all the way back to factory,I still had the bootloader unlocked/S-Off & TWRP installed,but,on the stock-unrooted ROM. Once complete w/the Device Unlock,I re-rooted & restored my ROM of choice. To a majority of users,this is a non-issue,most in the GP don't root/ROM,just wanted to save those who do the aggravation of attempting to unlock on a modified non-stock firmware. I'm guessing this applies to other mfgs w/the same Device Unlock app,IDK,YMMV,but,I suspect it's the same across all devices w/this app on-board.