I bought an iPhone 6 64 gab spring I need to unlock it?

I contacted sprint and the phone is paid off and everything but I can't unlock it because I don't have the previous users number what are ways I can unlock it don't post fake websites I already know all of them.

You don't need the previous user's number.

If you've bought an Activation Locked iPhone then you've just bought a worthless brick. If is not lost or stolen then the last owner has scammed you by selling it and then reporting it lost or stolen to make a fraudulent insurance claim; there's nothing you can do without the owners help to remove the Activation Lock.