iPhone dev team has release PwnageTool 3.1.4 which can jailbreak iPhone 2G/3G/3GS 3.1.2 and iPod Touch 1G/2G 3.1.2 where as geohot’s Blackra1n can jailbreak all iPhone and iPod Touch 3.1.2 OS.

In order to unlock your iPhone 3G & 3GS 3.1.2 you must use Pwnagetool 3.1.4 to jailbreak first and then use Ultasn0w 0.9 to unlock iPhone 3.1.2. If you have already upgraded to firmware 3.1.2 without preserving your baseband then you are out of luck.

Only iPhone3G & 3GS 3.1.2 users with baseband 04.26.08 can use Ultrasn0w to unlock iPhone to use it with any carrier. Below is complete guide on how to unlock iPhone 3.1.2.

How to Unlock iPhone 3G 3.1.2 & iPhone 3GS 3.1.2

1. Download PwnageTool 3.1.4 and follow iPhone 3.1.2 Jailbreak guide.

2. Once you have successfully jailbreak your iPhone 3G/3GS 3.1.2 go to Cydia and click on Manage Tab.

3.  Now select Sources and Click on Edit-Add to add following URL source

Http://repo666.ultrasn0w.com

And click on Add Source

4. After Cydia completes adding of source search for “ultrasn0w” in Cydia and install Ultrasn0w which will automatically unlock your iPhone 3.1.2 OS.

That’s it.