Instruction provided by iclarified.com

Phone | How to Unlock the iPhone 3G Thursday, 1st January 2009, 10:01 am These are instructions on how to software unlock the iPhone 3G for use with any GSM cellphone carrier.

Before you can follow these instructions you must have a jailbroken iPhone and you must be on the 02.28.00 baseband(modem firmware). This means that you must be running the 2.2 firmware. If you used PwnageTool to update to 2.2 from 2.1 you will have to re-jailbreak using a QuickPwn jailbreak tutorial for the time being.

To find your firmware and modem firmware(baseband) versions you can follow this tutorial. If you are not on firmware version 2.2 and baseband version 02.28.00 then you need to follow one of these tutorials before unlocking: Mac, Windows

[pic]Watch the Video!
For your convenience this tutorial is available in video format also. Click the Watch It button to view the tutorial!

Step One
Press to launch Cydia Installer from your SpringBoard.
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Step Two
Press to select the Manage tab at the bottom of the screen.
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Step Three
Press to select the large Sources button
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Step Four
Press the Edit button at the top right of the screen.
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Step Five
Press the Add button at the top left of the screen.
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Step Six
Enter http://apt9.yellowsn0w.com/ as the source url and press the Add Source button.
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Step Seven
Once the source has been added press the large Return to Cydia button.
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Step Eight
Press the Done button at the top right of the screen.
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Step Nine
Press to select apt9.yellowsn0w.com from the list of user entered sources.
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Step Ten
Press to select yellowsn0w from the list of packages
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Step Eleven
Press the Install button at the top right of the screen.
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Step Twelve
Press the Confirm button at the top right of the screen.