If you are using other Network Sim cards other than AT&T, this is only normal that it will ask for a PIN code to unlock the phone and use it with other network carriers. You have two ways to unlock the phone for using other network Sim Cards. 1. Contact AT&T You can contact AT&T and request for PIN to unlock the phone and use it with some other Sim cards. 2. Electronic Shop There are alot of Electronic repair shop that offers unlocking a phone to use other network carriers Sim card. There will be a small fee for them to unlock the phone, normally it will take up to 3 Hours before the phone get`s unlock to use other sim card.