Please make sure that phone is locked to AT&T, IMEI is not blacklisted and phone is out of contract. There will be no refunds otherwise.
Use
This service to check provider and lock status
The service is performed by having your iPhone's IMEI registered as unlocked iPhone on Apple's servers. One of the implications is that your mobile phone will remain unlocked after any future iOS upgrades !
Your iPhone's warranty is also unaffected since this is a factory unlock and there is no modification of your phone's software in anyway.
Our AT&T Apple iPhone unlock is the best and most straight forward solution available on the internet. All you need to do submit your IMEI number. Once we completed processing your order all you need to do is to plug your Apple iPhone with non-original sim card into your computer (PC or Mac) and run iTunes