If you are still some time away from fulfilling your carrier contracts, then you would be looking at carrier unlocking options for your iPhone 3GS. Now, your iPhone cannot be unlocked without jailbreaking the device, which in turn is risky considering that you could be voiding your warranty. But if you are determined enough, go ahead. Here are the steps.
- Firstly, if you are yet to jailbreak your iPhone 3GS, follow the step-by-step instructions to jailbreak iPhone 3GS using Redsn0w here.
- You will now need to hacktivate your iPhone 3GS without an original SIM. Click on the link to follow the SIM card activating procedure
- From the iPhone springboard, launch Cydia and then navigate to Manage -> Sources -> Edit -> Add. Enter http://repo666.ultrasn0w.com and tap on ‘Add Source‘
- Once this repo is installed, search for ultrasn0w 1.0-1 on Cydia and install the application. The application will unlock your iPhone so that it can be used with any carrier.
- Restart your iPhone. The unlocking procedure is complete.