how to backup everything.
by rigor
1) make sure iCloud is turned on for everything. calendar, contacts (especially contacts) notes, . everything.
2) back up your iPhone to iTunes. you can back up your iPhone to any computer running iTunes, but you can only sync to one computer.
3) make sure backup / sync photos (and videos) is checked. iCloud won't back up every single picture. unless you pay money. if your only copy
of a photo is on your phone and you erase it , it is gone forever. photo stream only keeps 1000 pictures. it is VERY IMPORTANT you back up all your photos
4) right click on the iPhone and click on transfer purchase . its their somewhere. this makes sure that your apps in your library are updated to the latest versions, and this also transfers anything you bought on the iPhone to itunes
5) remember. anything that is "synced" is not backed up, because its already in the library.
6) anything u bought is in iCloud (like apps) so if the worse case scenario happens you can redownload them for free. even banned apps
7) consider encrypting your backup. this lets iTunes restore your iPhones secure keychain onto a different iPhone.
8) the computer running iTunes must use the same iTunes account as the iPhone.
9) I've heard stories that books are not able to redownload. so make sure you backup your books to iTunes as well .
once you do this, it is safe to to erase your iphone
unplug the iphone
click on erase all content and settings.
enter your iCloud password and lock code
it will say welcome! and all that stuff. sometime it will say connect to iTunes.
connect to itunes
restore from the backup you just made
and then that phone should unlock and iTunes should tell you that the iPhone is now unlocked.
if it does not then maybe you can use DFU restore to rule that out. but its likely that your unlock code is BS and sprint is lying