To unlock your iPhone from its carrier, you'll likely need to contact your carrier directly to cancel your contract.

(Subscriber Identity Module lock) A function in GSM cellphones that restricts the phone's use to a particular cellular carrier identified by a SIM card. SIM locks are used to ensure subscribers finish ...

If you need to find out your iPhone's carrier without a SIM card installed, you can do so through the Settings app.

AT&T today said that customers can activate Wireless Account Lock, a new feature that will prevent unauthorized changes to a wireless account. With Account Lock turned on, account changes like billing ...