You can now unlock iPhone 4 baseband 04.10.01, or iPhone 3GS 05.16.02 baseband. Some websites are now offering permanent unlock for iPhone, that is independent of iOS versions. Negri Elelectronics brings a new method, remotely unlocking after receiving your iPhone’s IMEI code, which is permanent and lasts through firmware updates and other software modifications.
You can get it from here:
You have to send your device IMEI over to them to let them complete the permanent iPhone unlock. If you have preserved your baseband (with sn0wbreeze 2.5.1 or PwnageTool 4.3) to any of following, you can use ultrasn0w 1.2.1 to unlock iPhone on iOS 4.3.1:
Presumably Apple would not close this unlocking method in the future as it is the “official” way to remove a subsidy lock – if AT&T offered the carrier unlock, it would be delivered the same way.