Update: If you are interested in the legit unlock that is suitable for any iPhone baseband including 04.12.01 and 04.11.08 you can use official IMEI unlock service. Russia strikes back! Looks like Russian guys manage to successfully unlock iPhones by IMEI. The site imei-server.com offers iPhone unlocks for about $140 for any device on AT&T as long as it's not on the blacklist. You can check unblocking availability right on the site as they have IMEI information and iPhone/iPad unlock state check services. The both are pain and the last one is probably based on minicom's AT+ commands. Guys promise you a neverlock with possibility to update to any iOS and baseband version. And don't be afraid to lose your unlock as this method should work forever, unless you change the device.

This how the method works. Let's say you're an iPhone owner and you want to use their service it for $140. Yes, you want it. Then you have to report your IMEI to those guys and they will shortly answer you about unlock possibility. You send your iPhone to them, they do the trick it and send it back to you. The delivery time varies from 2 to 4 weeks. They were unlocking iPhones since 2011 but had a few months break due to service unavailability. But since January 2012 they continue with their business in beta mode. That means the service worked partially but all the "freed" devices stayed unlocked forever. Since April 13 they succesfully unblock all versions of AT&T iPhones (except for 4S model). Important note: If your iPhone is jailbroken - that's ok but you have to re-jailbreak once iTunes says it's unlocked and you receive the confirmation letter. Here are the examples of IMEI check of unactivated iPhone: iPhone 4 - 16GB Black ( 4.3.3 ) IMEI: 012418002****** Serial: 7T034****** Limited Warranty; 2010-08-21 / 2011-08-20 Sold to country: Norway Carrier: Not available

Here's the little instruction on how iPhone IMEI unlock works:

Step One: Order unlock. The availability of the native AT&T native SIM card isn't a must. Step Two: When the procedure is over you'll receive the unlock confirmation email to the address you've entered by registration. Step Three: Connect your iPhone to PC with any SIM card and launch iTunes for five minutes. You can also update the firmware to the latest version to get the process going. Important: After the device's activation the firmware should be clean (no jailbreak, no third-party apps). Step Four: The phone gets activated on your SIM card. Step Five: Plug it off from the PC and use. The device will find your carrier automatically. Here's the video proof (in Russian): I don't know what to advise about this unlock. It seems to be a reliable solution as there are lots of satisfied customers from Russia and from around the world but it costs $140. Isn't it cheaper to buy unlocked iPhone or to sell the locked one and buy 4S for instance?