Adrian Kingsley-Hughes for ZDNet:

Yesterday AT&T began to offer customers who have an off-contract iPhone the opportunity to unlock the handset so that it can be used on other carriers. It seems that quite a few of you jumped on the chance to have this done and have reported back to me with your tales of success (and woe).

Adi offers a few anecdotes about customer experiences getting AT&T to unlock their iPhones; it’s a new trend, but it’s not universally understood by AT&T customer service representatives, so you may need to exercise some patience.

Why unlock an off-contract iPhone? Going to T-Mobile might be one reason. Another is to travel internationally; you can use local GSM carriers without having to pay AT&T a dime in exorbitant international calling rates.