Custom Roming Galaxy s3 Frontier from att to tmobile

[Kolya Man]

have a gear s3 frontier:SM-R765A. I just switched to tmobile (great!) and I want to put the watch as a smartwatch line not just bluetoothed to my phone, and get it working on digits. I DESPERATELY need help for this as I am going to a trip to russia and want this setup (1 month from now)! Thank you