I couldn't unlock the phone before leaving on holidays. Went to an AT&T kiosk and purchased a new sim card. Got home, swapped sim cards, entered the code and had service right away! Not sure why I couldn't unlock at home, having followed all the given instructions. Would highly recommend! I was told by a salesman to try to unlock the phone before leaving on holidays, but it didn't affect my ability to quickly and easily unlock once I got to the States.