This is a complete tutorial to unlock your iPhone 3G baseband with Ultrasn0w in order to use any Sim card on your mobile. There are different steps you may have to follow in order to achieve the desired result, but currently iPhone 3G is fully exploited and you will be able to use your iPhone 3G with any carrier worldwide at the end of this 'how to'. Please remember that you are doing this at your own risk: we are not responsible of damage to your hardware or of data loss. Make a full backup of your data before continue.
Open 'Setting' application on your device, 'General', 'About' and read the 'Modem Firmware' version to identify the baseband of your iPhone 3G. Then click on the corresponding button below to show the custom step-by-step guide.
Your device must have iOS4.2.1 installed: check it on Settings application > General > About > Version. If you have a lower version open iTunes and click on 'Restore' button. Your device will be restored to iOS4.2.1 Official Firmware.
Download Redsn0w 0.9.14b2 on your computer.: Redsn0w
Open Redns0w: click on 'Jailbreak' button and select the 'Install iPad Baseband' option. Follow the instruction provided by Redsn0w. When the process is complete check if your baseband has been correctly updated to 06.15.00.
Download Apple iOS4.2.1 Official Firmware from this page: Original Firmwares
We assume that you have iOS4.2.1 installed on your device. If not, please use PwnageTool (MacOSX) or Sn0wbreeze (Windows) to create and install an iOS4.2.1 custom firmware, and then proceed. PwnageTool Sn0wBreeze
Download Redsn0w 0.9.14b2 on your computer.: Redsn0w
Open Redsn0w and click on 'Extras' button, then 'Select IPSW' and load the iOS4.2.1 Official Firmware previously downloaded.
Go back in the first window of Redsn0w and now click on 'Jailbreak' button and select the 'Downgrade from iPad baseband' option. Follow the instructions provided by Redsn0w. When the process is complete check if your baseband has been correctly updated to 05.13.04.