Below guide will help you on how to unlock an iphone, I was able to unlock my iphone easily within few minutes. After unlock you can use your iphone on any mobile carrier so it is in the state of carrier unlock. You must have to jailbreak your iphone before and you can jailbreak by visiting my Tutorial on How to Jailbreak.
Now I assume that you are having iPhone 4, iPhone 3GS or iPhone 3G that are already jailbroken on iOS 5.0.1, therefore we shall unlock iphone through recently released Ultrasn0w 1.2.5.
Note: T-Mobile USA users have to disable 3G network before starting unlocking iphone Go to Settings >General >Network and switch the “Enable 3G” switch to OFF.
UltraSn0w 1.2.5 Supported Basebands are as under:
iPhone 4: 01.59.00
Remember your device should be Jailbroken so that you can use Cydia for unlocking using UltraSn0w 1.2.5, you can visit this article to jailbreak now.
Steps for Unlocking are:
Step 1: Tap Cydia icon to start the application and tap Manage after Cydia loads.
Step 2: Tap Sources
Step 3: Tap the Edit tab as shown in below screen
Step 4: Tap the Add Button
Step 5: Type following URL and Tap Add Source
Download of Cydia source will be done automatically. After the source is successfully added to the Cydia tap return to Cydia button at bottom of the screen and then tap the Done button.
Step 6: Now you will be in the main window of Cydia if not just open it and tap Search at lower right corner (see image at step 3). Now type Ultrans0w in Cydia search box as shown below and tap the ultrasn0w as shown in below screen.
Step 7: After tapping you will see the below screen now tap Install and tap Confirm on next screen. The installation will begin and complete itself.
Step 8: Reboot your device.
Wow. your device is unlocked on iOS 5.0.1 try using the different SIM cards..