SIM unlocking United States

Most iPhones were and still are sold with a SIM lock, which restricts the use of the phone to one particular carrier, a common practice with subsidized GSM phones. Unlike most GSM phones however, the phone cannot be officially unlocked by entering a code. The locked/unlocked state is maintained on Apple's servers per IMEI and is set when the iPhone is activated.

While the iPhone was initially sold in the US only on the AT&T network with a SIM lock in place, various hackers have found methods to "unlock" the phone from a specific network.[213] Although AT&T and Verizon are the only authorized iPhone carriers in the United States, unlocked iPhones can be used with other carriers after unlocking.[214] More than a quarter of the original iPhones sold in the United States were not registered with AT&T. Apple speculates that they were likely shipped overseas and unlocked, a lucrative market before the iPhone 3G's worldwide release.[215] iPhones are unlocked by users who wish to use networks other than AT&T's.[10][not in citation given]

AT&T has stated that the "iPhone cannot be unlocked, even if you are out of contract".[214][216] On March 26, 2009, AT&T in the United States began selling the iPhone without a contract, though still SIM-locked to their network.[217] The up-front purchase price of such iPhone units is often twice as expensive as those bundled with contracts.[218] Outside of the United States, policies differ, especially in US territories and insular areas like Guam, where GTA TeleGuam is the exclusive carrier for the iPhone, since neither AT&T nor Verizon have a presence in the area.[219]