I live in the UK and have a friend visiting from the USA soon. She is tied to AT&T on her smartphone. What are her best and cheapest options for bringing her phone here to the UK and being able to use data, make calls, and send texts back to America?
Ideally looking for American experts who have travelled to the UK recently and have set up some kind of calling plan through AT&T that worked out well. Unfortunately international use of mobile phones is not my strong point.