Audiovox CDM-8615 / Vox 8610

hey guys. i'm phone challenged. my friend was playing around with my phone and set my phone so when someone calls, it doesn't vibrate or ring. i tried going to the settings menu and went to the place to turn your ringtone on or off, but i don't know what to press to make the ringtone come on. i tried pressing all the buttons, but the ringtone on sign won't come on. help me please!!!