The first thing you need to do is back up the data from your phone. Install Kies, connect the phone and create a backup or simply save the data from the phone. Then, on the phone, go to Settings > Backup and Restore > Factory Reset. This will re-install the operating system. It will be as if it is freshly released by Samsung. After this, try calling or playing an audio file in Music. If you still encounter the issue, then you might need to take the phone to warranty service or to a local phone service shop if it's out of warranty.