While talking about any mobile phones, the SIM unlocking means that you can now use any SIM card, from any carrier. This process in iPhone is very simple and not to forget the benefits of this process, you can use a local carrier while traveling, you can change your original pricing plans and take advantage of other mobile networks.
If you are an owner of iPhone 3G or 3GS, with the latest firmware installed on it, then you should be happy that there is a good news for you. Yes guys! You can now unlock the iPhone 3.1.3 safely without any efforts.
You should understand the fact that this process could damage your device. You must jailbreak the iPhone first, to gain full access to it.
Here are 5 simple steps to unlock iPhone 3.1.3 Firmware:
Step 1: Start “Cydia” and touch on “Manage” tab. Now touch on “Sources”. If you are using T-Mobile disable the 3G service first.
Step 2: Touch on “Edit” and “Add”. Type http://repo666.ultrasn0w.com when you are prompted to do so, now touch on “Add Source”.
Step 3: Search for ultrasn0w in Cydia and install it. This application will automatically unlock the iPhone 3.1.3 after installation.
Step 4: Restart your iPhone.
Step 5: Congrats! You have successfully unlocked your iPhone 3.1.3 Firmware!
via [Soft Sailor]