New version of Ultrasnow / ultran0w is now available for the iPhone which allows you to unlock iPhone with these basebands – 01.59.00, 04.26.08, 05.11.07, 05.12.01, 05.13.04 and 06.15.00. Before you proceed, please make sure that unlock for the newer baseband is still not available yet.
First, you will need to jailbreak your iPhone using pwnagetool. For that, feel free to check out my iPhone 4.3.3 pwnagetool jailbreak or the snowbreeze jailbreak guide.
Start cydia on your iPhone and go to Manage tab and then on Sources. Then tap on Edit and then on Add. Add “http://repo666.ultrasn0w.com” and then click on Add Source.
Search for “ultrasn0w 1.2.3” (note it is 0 = zero, not O). Install it and in the end of installation, you will have a perfectly unlocked iPhone.
Note that you must not follow this guide if you used iPhone 4.3.3 redsnow jailbreak guide to jailbreak your iOS device.
Running iOS 4.3.1, check out iPhone 4.3.1 unlock guide.