You can use any phone from t-mobile but you will first need to unlock the phone. It is usually better to purchase the phone already unlocked. If you want to buy a t-mobile phone and use it for ATT then you can either go to a cell phone store to get unlocked, depending on location could cost anywhere from $25 to $65. Or if you purchase the phone at a t-mobile store and pay full retail price you can fax the receipt to t-mobile and they will unlock the phone for you.
O it will fit into all of them... a sim card is a sim card. but you wont be able to use it. It has to be an at&t phone or an unlocked phone. There is softwear that you can buy to unlock the phone yourself or you can just buy it already unlocked on ebay or amazon.
hi until you you unlock your mobile from network your cant use other network sim in it . to solve this you must unlock your mobile .codes are the best solution to unlock your mobile .to get codes visit simpleunlocking.com here they ask the imei number of your mobile .finally they deliver you codes to unlock your mobile.