How to unlock a Sprint iPhone with the factory unlock code?

So i'll be calling Sprint in a couple days to get the factory unlock code for my iPhone 4S once i'm donw with my contract, so what do i do next with that code to factory unlock the phone? And eventhough it's unlocked could it still only be used with Sprint or Verizon (since it's a CDMA phone) or can it now be used with networks like AT&T or tMobile?

1. Obtain the Master Subsidy Lock (MSL) code for your phone. You often can get this code simply by calling Sprint customer service; the code is technically yours. The MSL is required for many Sprint-approved purposes, such as resetting your phone to factory default settings.
2. Press the pound symbol (#) twice from your phone's dial screen. Enter "332846368," which corresponds to "DEBUGMENU." Finally, press the pound symbol again.
3. Enter your MSL code.
4. Select the "Toggle NAI" option from the menu that appears.
5. Switch your "Toggle NAI" setting to "Off."

I have an Iphone 4S from Sprint and they gave me the Master Subsidy Lock Code. However, when I enter the information above, the Toggle NAI option menu does not come up?

I had to write FCC before they (sprint)would release the code. They put me through the ringer