Before you start, you must have a jailbroken iPhone if you haven’t jailbreaked your iPhone 3G then follow our Guide Jailbreak, Activate iPhone OS 3.0 With RedSn0w. For unlocking your iPhone UltraSn0w, a soft unlock payload from iPhone Dev Team is using. UltraSn0w is a small daemon that is launched on boot. It injects the payload at boot and also whenever there is a baseband reset. Which is quiet similar to what Redsn0w did. You won’t notice anything about it other than that all Networks now work. Once you have a Jailbreaked iPhone then you can use these easy stepsto Unlock.
Why Ultrasn0w for 3G when REdsn0w unlocks iPhone 3G?
If you are using a 3G iPhone with yellowsn0w and rely on yellowsn0w to obtain cellular service, then you should NOT use redsn0w. Ultrasn0w (the 3G carrier unlock) is not included with redsn0w and therefore your baseband will be locked and unable to use an operator other than the official one it was bought for.
2. Yellowsn0w in its current form will NOT work with the baseband version that is present in the 3.0 update, you will need Ultrasn0w, Ultrasn0w will work with all iPhone 3G models (but not 3GS), even ones that were previously unlockable, Ultrasn0w.
If you are done with redsn0w, please proceed as below:
1. Launch Cydia Installer, Select the Manage tab at the bottom of the screen, then click the Sources button
2 : Click Edit at the top right & then Press the Add button at the top left. Enter “http://repo666.ultrasn0w.com/” in the source url and click the Add Source button. Now cydia would validate the supplied URL, check for updates in the source URL mentioned
3 : Once the source has been added and updated, click the Return to Cydia button. Press the Done button at the top right of the screen.
4 : Touch to select http://repo666.ultrasn0w.com/ from the list of sources.
5 : Touch to select ultrasn0w from the list of packages.Press the Install button and confirm. After installation completes successfully press the large Return to Cydia button, restart iPhone.
6: There is no step 6, Your iPhone 3G should now work with any network.
Dev Team Rocks!