sound wont work but vibrate will

  I got this from someone who works at verizon i traded a blackberry for it, because i hve 2 lines and can't afford the data package with the other line just sitting on my dresser, anyways i activated it, and my vibrate works but my sound all my sound does not work, the volume, the ringtones, nor my alarm, i tried the service thing to test it but i hear nothing. does anyone have any advice for me? im frustated thanks in advance

shi