In a recent shift, a report suggest that AT&T will change its policy in regard to unlocking iPhones out of contract. The reports tates that starting Sunday, customers with an account which is both in good standing and out of contract will be able to request a carrier unlock code for their iPhones.
An unlocked iPhone will allow you to use it with any SIM / microSIM card. AT&T issued the following statement in regard to this report:
Beginning Sunday, April 8, we will offer qualifying customers the ability to unlock their AT&T iPhones. The only requirements are that a customer’s account must be in good standing, their device cannot be associated with a current and active term commitment on an AT&T customer account, and they need to have fulfilled their contract term, upgraded under one of our upgrade policies or paid an early termination fee.So if you are holding onto a locked device best head over to AT&T on Sunday to get your old iPhones unlocked and free.
source - Engadget | MacRumors