A:Answer if you buy through the your carrier it will be locked to the carrier until the device is Paid off, if you buy from best buy apart from the carrier " UNLOCKED" it will lock to the initial SIM card that you put into it. so if its ATT , it will automatically lock to ATT , and you can request to have the device unlocked since you purchased from a 3rd party retailer. as Long as you are not on a carrier Installment plan you can have the device unlocked. you can also buy directly from apple and finance the device with Apple. the device will be called SIM free and will work with almost all global carriers and you are not TIED to any carrier. don't buy the device from Best Buy if you are going to take it overseas before unlocking it from the domestic carrier or you will have issues and the phone will be unusable overseas. I hope I explained this correctly. good day,