There are a few options open to you to unlock your iPhone 3GS, including a free method. Please note though that jailbreaking and unlocking your iPhone yourself can casue issues with software updates, and will void your warranty. Find out more about unlocking your iPhone 3GS free below.
If you're not comfortable with unlocking your iPhone yourself, there are a number of additional options open to you. Firstly, you can ask your current network provider to unlock your iPhone 3GS - they do this via iTunes and the process normally takes around 48 hours.
If your current netowrk provider can't help you unlock your phone, you can also try a number of third party companies who can help. To find a company who can safely unlock your iPhone, simply select your current network from the dropdown list below and you will see a list of providers who unlock the 3GS as well as the times and prices for the unlock.
If you use one of the listed services, please let us know how you found the service int he ratings and comments sections as this helps others in the future. Or tell us about another method you've used to unlock this phone.
*Please note that prices to unlock may vary according to the network you're currently on.
Unlock the iPhone 3GS yourself for free
If you have an iPhone 3GS it is pretty easy to unlock for free. It involves a process known as jailbreaking (opening up the software on your phone) and then running some additional software to perform the actual unlock.
The first thing to do is to check that there is an available unlock for the version of iOS and baseband (modem firmware) that you are using, or that there is a downgrade to a supported baseband. To check your iOS version and baseband, go to Settings > General > About on your iPhone.
At the time of writing the latest version of iOS with an available untethered jailbreak and unlock is 5.1.1 (using ultrasn0w 1.2.7) providing you are on one of the following baseband
iPhone 4: 01.59.00
iPhone 3G(S): 04.26.08, 05.11.07, 05.13.04, 05.12.01, 06.15.00*
Once ultrasn0w 1.2.8 is released, a jailbreak and unlock will be available on iOS 6.x on the same basebands listed above. Check the iPhone Dev Blog for updates.
Redsn0w is available from the iPhone Dev Blog
Ultrasn0w is available on Cydia by adding to the list of sources.
* Baseband 06.15.00 is an iPad baseband, and disables the GPS receiver. If you have already updated to 06.15.00 to unlock, there is a baseband downgrade available using redsn0w (0.9.15b1). If you are going to downgrade, you must make sure that you have a compatible model iPhone 3G(s), as newer models have a fixed baseband. Follow the instructions on redsn0w very carefully