Only AT&T can do it. You might get a reply from someone inside AT&T's unlocking dept to do it for you on the side, but they'd probably lose their jobs pretty quickly.
Originally Posted by UnlockMagic
Unlocked iPhone 5, unlocked iPhone 4
Unlimited airtime, Unlimited CAN/US long distance, Unlimited SMS to CAN/US wireless numbers
2500 Call Forwarding minutes to CAN/US numbers
Google Voice for visual voice mail with message transcription, conditional greetings, unlimited messages (vs 35 message cap), remote retrieval from any PC or phone, no auto-purge after 10 days and most importantly no $7-$8 charge.