The iPhone Dev Team had only recently announced that their carrier unlock for iPhone 3G and 3GS phones are now available with RedSn0w 0.9.6b5 and PwnageTool 4.1.3. As we had noted already, the unlocking process involves updating the baseband of your iPhone to the original firmware of the iPad that is incidentally vulnerable to an existing exploit.
If you are having trouble with the instructions from the Dev Team website for the baseband upgrade, here is a nice video walkthrough above from RedmondPie of the entire process that you can check out in the video below. The video goes beyond baseband upgrade and take you through the complete RedSn0w unlocking process.
But before you proceed, we must warn you that the entire process is quite risky and you risk not just bricking your iPhone but may also void your warranty. So, it goes without saying that the risk is upon you.