How to unlock a Sprint iPhone 4S?

I want to be able to use it with other carriers, but I'm not sure how. I have heard of using the GPP sim but I'm afraid that if I update it, the phone will re-lock and I would have to purchase another GPP sim. I've looked up other methods of unlocking a Sprint iPhone 4S, but they're terribly expensive - around 100 dollars!

Does anyone know any way to unlock it for a cheap price, or even free? Any help is appreciated. Thank you!

Added (1). IPhone 4S can be used for both CDMA and GSM. I think you're talking about the iPhone 4.

A Sprint phone doesn't have a sim, and it can only be used on a CDMA carrier. Sprint and Verizon are the largest ones.

Unlocked or not, it will only work on sprint

I've read in some places that if you call the carrier and say you're going out of the country and need it unlocked they can do it. And if that doesn't work call again and say you demand your phone be unlocked. As long as you're not in any sort of contract, I don't see why they wouldn't.

Hi, you can get it unlocked easily by using the Remote Unlocking Service. I unlock form http://iphonejailbreak-unlock.com, you can unlock your too and price is only $19.95. This is only lowest i found.