The majority of your monthly use has to be on Tmobile towers and if not Tmobile will cancel your
account for excessive roaming.
gramps is correct!
1 of 1 people found this helpful
They can cut you off for excessive roaming. It's not automatic. Your account gets flagged and then someone looks at the usage. Maybe if a lot of your usage is on WiFi and you don't use it much, they'll let you slide, maybe not. My suggestion is that you unlock your phone and port your line out to Google Voice. Get a local prepaid SIM for your phone and take your US calls via Hangouts. When you return to the US, port your line from Google Voice to whatever mobile carrier serves you best at the time.
What phone do you have now? Is it locked our unlocked?