Those are the same company. ._. T-mobile and AT&T are the only ones that have sim cards as said in the Cellphone frequently asked questions
QUOTE
Unlocked Phones
Which carrier can I use with an unlocked phone?
- In America, T-Mobile and AT&T.
- In Canada, Rogers and Fido.
- In Europe, T-mobile and Vodafone, and O2. I actually think all carriers in Europe use GSM, but I'm not 100% sure.
What is an unlocked phone?
It's a phone that can be used on any carrier that use GSM bands and SIM cards.
What are SIM cards?
SIM cards are the little cards that are in the back of your phone. Take the battery cover off then the battery off and you should see a white card, or different color depending on carrier. Here's a picture for visual purposes.
Will "this" unlocked phone work with my carrier?
It depends on the carrier. Each carrier uses different bands, in America anyways. I'm sure carriers in other countries use the same band. If you don't know which band your carrier uses. Simply ask them or google.
So many questions could be answered in this thread if people actually read the FAQ's. ._.