Q: My mute switch does nothing

The mute switch on my iPhone 4 doesn't do anything. It worked fine previously but now when I flick the switch literally nothing happens. Nothing comes up on the screen and my calls/texts/email notifications aren't silenced. Does anyone know if there's anyway to fix this without sending it in for repair? I'd like to avoid that if possible as I require my phone for work, but the constant notification sounds drive me crazy.