Q: Notification sound is the same for all apps!

This has been driving me up the wall ever since I got my iPhone.

whenever I get a notification for a tweet, facebook notification, instagram, doesn't matter what app, it's the same sound, I went into the "sound" and "notification" center on the phone and changed all the notification sounds personally, and it's not working whatsoever, I have tried turning it on and off, and it isn't working.

Please tell me what to do, this is driving me crazy!