My iPhone 4 won't come off silent mode when flicking the switch on the side?

The phone does sound e.g. Music.

Seeing as your warranty will have expired by now you can do one of the following.

1. Go to Apple, and pay for repairs

2. Attempt to repair the phone yourself by using online instructions.e. G.:

3. Go to "settings". Then accessibility. After this go to "AssistiveTouch" and switch it on.
A white electronic button will appear on the screen. Press on it. Then press "Device" and "Mute"

There you go! Hope this works!