If this applies to you, you’ll want to use PwnageTool 4.3.3 (Mac) or Sn0wbreeze (Windows) to jailbreak while preserving your old baseband and updating to iOS 4.3.3.
Install Ultrasn0w Unlock for 4.3.3
After you are jailbroken, ultrasn0w is installed through Cydia. You can generally do this just by searching for “ultrasn0w” but if that fails:
- Add http://repo666.ultrasn0w.com as a source repository to Cydia
- Search for “Ultrasn0w 1.2.3″ and install
- Reboot your iPhone