Unlock the iPhone 3G

This article teaches you how to unlock an iPhone 3G so it can be used on any GSM carrier network.

Steps

Connect your iPhone or iPad to your desktop. Use the USB cable that came with your device.
- Tap Trust on your device's screen if prompted after connecting.
Open iTunes. Do so if iTunes doesn't launch automatically when you connect your device.
Click on your device's icon in the top bar of the window. It may take a moment to appear.
Click on Back Up Now. Before updating, it's always advised to create a backup in case something goes wrong. This should only take a minute or two, and will allow you to restore your iOS device if an error occurs during the update process.
Click on Check for Update. You'll see this on the Summary page after selecting your iOS device.
- iOS 4.2.1 is the most recent Apple-authorized update available for iPhone 3G.^[1]
- You may be prompted to update automatically when you first launch iTunes with your device connected. You'll see a notification if your device is already up to date.
Click on Download and Update. This will download the update to your computer, and apply it to your iOS device. This process may take a while, and you can monitor the progress of the update on your device's screen.
Finish the update process. After the update has been installed on your iPhone, you'll need to complete it by entering your passcode or signing in with your Apple ID.
Jailbreak your iPhone. Use the Jailbreak-an-iPod-Touch-or-iPhone-3G-on-a-3.1.3-Firmware but select the Redsn0w version that is compatible with iOS 4.2.1.

Open the Cydia app. It's a brown app with a white, open box icon that was installed during the Jailbreak-an-iPod-Touch-or-iPhone-3G-on-a-3.1.3-Firmware.
Tap Sections. It's an icon in the upper-left part of the screen.
Scroll down and tap Utilities. The folders are listed alphabetically.
Tap Ultrasn0w. It's listed alphabetically in the folder.
Tap Install. It's in the upper-right corner of the screen.
Tap Confirm. It's in the upper-right corner of the screen.
- Wait for Ultrasn0w to configure.
Tap Reboot Device. It's at the bottom of the screen.
- Once your device reboots, you can Put-a-SIM-Card-Into-an-iPhone to make calls and access data on your iPhone 3G.

If you wish to restore your iPhone to its factory settings after unlocking, use the Restore button in iTunes. Please note, you will lose all personal data, information and applications. You will no longer be able to use applications that were available on your jailbroken iPhone.
Apple frequently includes in iOS updates "plugs" for software holes exploited by jailbreak programs. After jailbreaking your iPhone, do not use iTunes to update your device. Check the Dev-Team Blog frequently to determine when and where you should download updates for your device.

Jailbreaking and unlocking an iPhone are not activities sanctioned by Apple or any of its service partners. If you experience difficulties with your iPhone after unlocking, you must restore it to its factory settings prior to bringing it in for service. While jailbreaking and unlocking an iPhone is legal, Apple considers these actions violations of their end-user license agreement and may deny any service claims.