HOW TO: Downgrade 06.15.00 Baseband to 05.13 on iPhone 3G
Most of iPhone 3G and iPhone 3GS users updated their baseband to iPad's one which is 06.15.00 to be able to unlock it. It's not possible to restore using stock firmware on iPad's baseband so you can downgrade to baseband 05.13.xx which is unlockable using ultrasn0w and you'll be able also to restore using stock firmware on this baseband.This method...