How to Unlock iPhone 3GS Baseband 5.16.02 on iOS 4.3.3?

Hello Lowell, yes, you will be able to jailbreak and unlock your iPhone 3GS on iOS 4.3.3 and use it over other mobile phone carrier. However, there are few things that you need to know in order to jailbreak and unlock it. First, you should be noted that the only way to unlock iPhone 3GS is by updating its baseband to iPad’s 6.15.00 baseband. However, this process has a downside; you will automatically lose the GPS functionality of your device, and at the moment, there’s no available fix for this issue. In addition, once you have iPad baseband installed on your device, there’s no way you can upgrade or downgrade your baseband. Meaning, you are stuck at this baseband, this also means that you will not be able to restore your iPhone to the stock firmware in the future software update.

Anyway, to prepare your iPhone for unlock as well as to install iPad baseband on your device, you can use Redsn0w 0.9.6RC19. You can get Redsn0w 0.9.6RC19 for Mac OS X using this download link (Windows version of Redsn0w 0.9.6RC19 can be download from here). Once you have download Redsn0w, you can now jailbreak your iPhone 3GS as well as update its baseband by following this tutorial. Lastly, once completely jailbroken with Cydia and iPad baseband installed, you can now unlock your iPhone using Ultrasn0w 1.2.3. The details instruction on how to unlock an iPhone using Ultrasn0w can be found on this blog post.