[jim180]

No idea, but Tello always worked outside of the U.S - Lithuania in my case.

I guess, provider will always consider your country where the phone number is located. Funny thing, while I'm roaming, my IP address will always be Lithuanian. It does not matter where the world I'm currently staying.

[onlygoose]

This is the major way roaming is implemented, transferring all data through your home network greatly simplifies things.