After long-wait and suspense iPhone Dev Team has finally released the only software unlock for iPhone 3G, the unlock is available via Cydia installer for iPhone and is known as yellowsn0w, the application is a small daemon without any GUI which gets launched on boot injecting the payload, here are step-by-step instructions on how to get the 3G unlock working on your device.
- Download and install iTunes 8.02 or later from Apple website here.
- Connect your iPhone, if you have not upgraded your iPhone to firmware 2.2 you will be asked to do so, download and install the iPhone 2.2 firmware upgrade following the on-screen instructions.
- After updating to iPhone OS 2.2 you should be having iPhone baseband version 2.28.00, which is required to get this unlock work.
- Download QuickPwn 2.2 and 2.2 IPSW file for Jailbreaking your iPhone 3G.
- Launch QuickPwn 2.2 and follow on-screen instructions to Jaibreak the iPhone and install Cydia.
- Now connect your iPhone to WiFi and launch Cydia, add these new sources :
Here is how you add source to Cydia.
- Now check Changes tab in Cydia and yellowsn0w should be on top, Install yellowsn0w and Run it.
- Restart iPhone and your phone should be unlocked.
If the above process fails you can check the user-submitted operator specific instructions posted here.