My iPhone 4 doesn't make sounds.

Since yesterday my iPhone stopped making sounds from alerts and clicks from the keyboard but I know the speakers work because when I go to Settings-Sounds and I move the volume bar it rings. I'm already sure that the Lock sounds, Keyboard clicks and alerts are ON, but still doesn't work. Also, when I try to turn up the volume with the volume buttons on the iPhone it doesn't work. It shows the ringer icon but with no volume bars. It's frustrating because I never notice whenever I get an alert. I already cleaned all the dust in the dock connector and in the headset jack. Also tried plug and unplug the headphones, still not working.

I didn't drop the iPhone, neither spilled anything on it. It just suddenly stop working correctly.

I already restored the iOS 5.1 software but didn't work.

It only works with the headset.

Hope somebody knows the solution 😟.