It is possible to unlock your blackberry torch from At&t and can use T-mobile..try mobileunlocksolutions to get mep2 code for your blackberry curve 8520 and get it unlocked..
Yes it is possible to unlock your blackberry torch mobile by using unlock code. If you need unlock code you can visit this site UnBBLock.com here you can get the unlock code and unlock your mobile easily. After unlock your mobile you can easily swap from a&t to t-mobile network.