To settle a class action lawsuit, AT&T has agreed to provide unlock codes for all of its phones, with some notable exceptions. First, a customer must complete 90 days of active service. Second, a customer must have a proof of purchase for the phone. Third, if AT&T has an exclusive hold on the phone for less than 10 months, customers have to wait until that 10 month period expires. This also means that if AT&T has a longer exclusive period, the carrier will never provide an unlock code. Presumably, the only handset family to which this caveat applies is the iPhone, so iPhone owners will not be able to port their handsets to another carrier, such as T-Mobile.

Source: Phonescoop