Iphone 4 sound problem, help?

Hello, basically I have the Iphone 4, and im having such an annoying problem with the sound and cannot find a solution anywhere!

When im using my phone to listen to music or speak on the phone, my volume works perfectly, no problems at all, yet when i go to on any of my apps NO VOLUME whatsoever, also my phone doesnt make a noise when someone rings or messages me, its not on silent, ive checked all the settings aswell,h

when i press the volume buttons on the side of the phone the volume doesnt change, it doesn't even come up on the screen that its going up or down, same when i switch it from silent mode, to non silent mode.

ive tried reformatting the device, also updated to 1S07, this problem is still happening.

someone has to know what to do right?! hahaha.

Thank-you in advance...