How to unlock Iphone 3g,3gs

Ingredients:

• An iPhone 3G/3GS updated to firmware 4.2.1, which meets the above requirements.
• Firmware version 4.2.1 for iPhone 3G/3GS
• iTunes 10.1 or later
• redsn0w 0.9.6b5 for Mac.

1st download custom firmware

http://www.ulozto.net/x3HRbs1/iphone-3g-custom-firmware-4-2-1-8c148-ipsw

or http://uploading.com/files/get2/2c19b542/1?

2  download redsn0w - http://redsnow.biz/

Install Redsn0w and open it.

 Click the ‘Browse’ button below the text, it will ask you to locate a firmware file, choose the 4.2.1 firmware for your device and click ‘Open’.

 After it says ‘IPSW successfully identified’, click the ‘Next’ button located near the bottom-right and it will download some jailbreak data from the server.

click install Cydia 

Optional - If you read the warning above and still want to unlock your iPhone 3G or newer iPhone 3GS, choose ‘Install iPad Baseband’. It will again ask if you really want to use the iPad baseband, click ‘Yes’ and click the ‘Next’ button again.

Now, it will ask you to connect the device to your Mac/PC and then turn it off, do so and click ‘Next’. Now follow the on-screen instructions to proceed.

The device will reboot a couple of times showing ‘Downloading Jailbreak Data’ logo on the device’s screen, while redsn0w sends modified files to the device. When redsn0w is done, click the ‘Finish’ button and let the rest of process continue on the device, please be patient.

1. 
   Launch the Cydia application on your iPhone and search for ultrasn0w. Once found, install ultrasn0w on your device. If ultrasn0w doesn't appear in your search results, follow these steps:
   • Click the "Manage" button on the Cydia home screen and then select "Sources."
   • Click "Edit" and then "Add."
   • Enter "" http://repo666.ultrasn0w.com" into the Cydia/APT URL field and click the "Add Source" button.
   • Once Cydia verifies the URL that you have entered and registers the repository URL, return to the Cydia homescreen and continue installing ultrasn0w.