Q: IP6 for Tmobil

Hi there unghuynh2014,

You may find the information in the article below helpful.

iPhone and iPad: Using cellular networks while in another country 

Many carriers offer international voice and data plans. Always contact your current carrier for details about international-roaming countries, SIMs, rates, and policies before you travel to another country. While you may not need an international plan to use voice or data roaming on your iPhone or iPad, your carrier may charge additional fees or higher data rates if you don't have an international plan. 

-Griff W.