Jailbreaking/unlocking the 3G S iPhone using redsn0w
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Step 4.
Let's unlock the iPhone now. Launch Cydia. You'll be greeted with this message. Cydia will then close. Launch Cydia again. You'll be greeted with this message. Make your choice. You can always change it later. Note: Ignore the AT&T logos in these screen shots if you have an unactivated iPhone. This will still work.
I recommend performing these upgrades. Once they have been installed, Cydia will close again. Launch Cydia one last time. Press the Manage button, then press Sources.
Press Edit, then press Add.
Enter repo666.ultrasn0w.com then press the Add Source button. The source will be checked and added. Press Return to Cydia.
Press Done. Then press the source name.
Press ultrasn0w. Press Install.
Press Confirm. When it has finished installing, do not press the button that says Reboot Device! Instead, press the Home button.
Launch Settings. Press General, then press Network. Make sure Enable 3G is set to OFF (unless the carrier you want to use supports the same 3G frequencies the iPhone uses). Go back to Settings, and turn on Airplane Mode. Turn off the iPhone.
Step 5.
Switch out your SIM cards.
Step 6.
Turn on the iPhone. Turn off Airplane Mode. It may say Searching... for up to a minute and a half until it finds your new carrier. In my case it didn't find my carrier, and said No Service. Also note my Wi-Fi network name disappeared for whatever reason. The carrier menu appeared. I pressed this.
A minute later, this menu appeared. It's set to Automatic by default. I've heard it's best to set this to the carrier you intend to use. You may have better results if you do. I then pressed T-Mobile. 2 minutes later, the check mark appeared next to T-Mobile.
Note: If it says Off (in gray) next to Wi-Fi, do this to fix it: from this menu press General, then press Reset, then Reset Network Settings. The press Reset Network Settings at the confirmation screen. You'll get the spinning wheel on the SpringBoard for a minute and the iPhone will reboot. All should be well.
The About page will display that you are now unlocked and on 3.0.1 firmware and on the latest modem firmware. Note: I erase my iPhone's personal hardware specs from these screens. Yours will have values there.
For more information on ultrasn0w, and any perceived issues, or conflicts, read this post by the iPhone Dev Team.
Should you have issues with Push notifications or ultrasn0w dropping your cellular signal, read this post by ranova over at BigBoss.org
The iPhone will reboot again. iTunes should ask you to set up your iPhone. Note: Many people find that they have problems with their applications crashing when they choose "Restore from the backup of" at this screen. If this happens to you, your only option may be to repeat this entire process then choose "Set up as a new iPhone" and resync your iPhone instead. You will of course lose application specific data.
iTunes will confirm you are on 3.0.1 firmware.
