This article is a guide on how to unlock your iPhone 4 and iPhone 3G/3GS. You will need to use Sn0wbreeze for Windows or RedSn0w, which is compatible with Windows and Mac OS X to preserve your baseband when updating to iOS 6.1
UltraSn0w 1.2.8 Supported iPhone Basebands
iPhone 4 on baseband 01.59.00
iPhone 3G/3GS basebands 04.26.08, 05.11.07, 05.12.01, 05.13.04, and 06.15.00
*In order to see if you have one of the supported basebands on your iPhone 4 or iPhone 3GS you will need to go into the Settings.app > General > About and look for the Modem Firmware field.
Unlock Your iPhone Running iOS 6.x Using UltraSn0w 1.2.8
Step 1: As mentioned previously you must already be running iOS 6.1 on your iPhone 4 or iPhone 3G/3GS, and you must also be Jailbroken on iOS 6.1. If you are yet to Jailbrake your iPhone then please click the appropriate platform.
Step 2: After your iPhone is running the iOS 6.1 firmware and is Jailbroken you will need to simply launch Cydia from your SpringBoard.
Step 3: Once Cydia is open you will need to tap Manage > Sources > Edit > Add. Normally the Ultrasn0w repo is there but if not add the below repo.
Followed by the Add Source button.
For a list of must have iOS 6 Sources, click here.
Step 6: After Cydia has refreshed. Tap the Search tab on the bottom tab bar and search for UltraSn0w. Once UltraSn0w appears, tap on it and you should see version 1.2.8.
Step 7: When UltraSn0w has installed you must restart your iPhone. Once restarted, plug in your unofficial SIM card and wait for your iPhone to connect to your network.
And there you go, all done.
If you have any further queries, problems or just general questions post a line in the comments section. Keep updated with new and upcoming releases by following our Twitter, also don’t forget to check back to iJailbreakthis for more updates.