Had an odd one, I arrived in Mexico, D.F. and got a text message welcoming me to Mexico and informing of the Voice/Messaging/and DATA Rates Per MB when I was under the impression that Mexico was like many other countries I have visited where DATA was 2G speeds but was free.
I used my phone like I have in many countries and have yet to see any roaming charges for DATA from T-Mobile yet, but had a small fright from the text message from T-Mobile and the fact that the DATA felt much faster than I am accustomed to while roaming with T-Mobile Internationally (like LTE fast).