The unlock tool ultrasn0w has just been updated to version 1.2.8 thanks to iPhone dev team member Sherif Hashim. However, this update is compatible with iOS 6, 6.0.1, 6.0.2, 6.1 on older basebands only and does not unlock the new baseband versions. If you don't know what ultrasn0w really is, it is a free unlock tool so you can use your iPhone with any carrier of your choice. Read more for the complete guide with images.