Unlock iPhone 3G – HowTo guide

Now you can unlock your iPhone 3G and can use it with any mobile service provider.iPhone Dev-team had announced that the “Yellowsn0w” ,the iPhone 3G soft Unlock tool ,is now available for download .
Yellowsn0wis the world’s first software unlock for the iPhone 3G. With yellowsn0w you can unlock your iPhone 3G firmware 2.2 .

Here is a quick guide to unlock the iPhone 3G:

• You need to install the latest 2.2 firmware (downloaded from here).

• Jailbreak your iPhone, using QuickPWN 2.2. Those using MacOS 10.5.6 need to re-enable DFU mode, which Apple disabled as a way to prevent Mac owners from jailbreaking their iPhones.

• You can install yellowsn0w 3G unlock by using either Cydia or Installer, add the following addresses to add yellowsn0w to your installer application:
  • For Cydia enter: http://apt9.yellowsn0w.com/
  • For Installer enter: http://i.yellowsn0w.com/

(source)For details refer http://www.crunchgear.com/2009/01/01/how-to-unlock-your-3g-iphone/