Technically, it is not easy that unlock an iPhone
updated to iOS 4.1,unlock option is not provided,for the iOS 4.1
baseband. But now it is possible,that you can unlock your iPhone.
If you are still using iOS 4.0.1 (may be earlier version 3.1.3), for this purpose you can use PwnageTool to jailbreak your iPhone it is presenting the baseband..That will make your iPhone to the latest iOS version,remember that do not update the baseband, because it is the key part of unlocking your
iPhone…
If u already have to updated to iOS 4.1 and upgrade it to baseband then can not unlock the iPhone.There probably would not any unlock for iOS 4.1 and you will to have a wait for the iOS 4.2.
Now ,time to tell you how you can unlock your iPhone
4.1 with UltraSn0w. This will work for the iPhone 4, iPhone 3GS, and
iPhone 3G.
Step 1: First check that you are still, on the iOS 4 or iOS 4.0.1.
Step 2: Upgrade your iPhone to Jailbreak use with the PwnageTool.
Step 3: Find the Cydia and search the UltraSn0w. Download and install UltraSn0w.
Step 4: Shutdown your iPhone.
Now all the procedure is Done!
An iPhone is unlocked with the UltraSn0w.