Moved the above post here to where the answers are
Here I've quoted what will help you
"2Gs and 3Gs on 3.1.3 can be jailbroken, and only unlocked if the bootloader is 5.08 or below. If you did an official itunes update to 3.1.3 there is pretty much no chance your bootloader is the correct version and you're probably locked do ATT till an unlock comes out. But they can be jailbroken.
use this link to jailbreak your 3.1.3 2G or 3G iphone:
http://www.redmondpie.com/download-s...-iphone-3.1.3/"