Why isn't the volume working on my Samsung Blackjack II?

All of a sudden today, the volume started acting strange on my phone. Whenever I receive a text or a call, the text message alert and/or the ringtone sounds really choppy. It doesn't ALWAYS happen, but a lot of the time, it does. If I turn the phone off and back on again, it works for a little bit, but then it reverts back to the same problem after a few minutes. Does anyone have any suggestions for how to fix this?