Since iPhones are only available to AT&T customers, finding a way to unlock or "jailbreak" an iPhone for use on other carriers is all the rage. This tutorial will show you how to jailbreak an iPhone with 3.1.3 firmware.
How to unlock the iphone 3G on 3.1.3 . The first thing you have to do is download Sn0wbreeze V. 1.5 which you can download from here ih8sn0w.com and also download Apple's original 3.1.3 ipsw file which you can find here www.felixbruns.de once you have both of those create your own custom 3.1.3 jailbroken Firmware . Use the custom Firmware you just created to jailbreak your iphone 3G. Once your iphone is jailbroken on 3.1.3 go to Cydia and install FUZZYBAND after you install it get out of Cydia go to your home screen on your iphone and go into FUZZYBAND once in there see if your bootloader from factory is 5.08 if it is your in luck click on where it says to DOWNGRADE your baseband once FUZZYBAND is complete it will tell you that you are ready for ultrasn0w . Go back into Cydia search for ultrasn0w and install this will automatically unlock your phone. And there you have it your iphone 3G on 3.1.3 Firmware with 04.26.08 baseband Unlock ..