IPhone :: Low Call Volume On 4?

I have a strange problem on my iphone.It was mentioned in this forums but none of them solves my problem.1.Problem:While making a call, I can barely hear the voice from the headset. Call volume is max ( also the system volume ) yet it is still too law. There is no plastic cover on my iphone. I have restored the phone to IOS 5.1 yet problem stands still and it is really annoying.2.Problem: While recording a video with the default camera app, sound is not recorded. That is very strange because my mic works quite fine during the calls. When I use a third party video recording or sound recording app from the app store sound is being recorded without any problem yet with the default camera app I can hear some noise only when i tap on the mic with my finger but no sound. This should be a software problem yet restoring or upgrading to the new firmwares hasnt solved the problem.

3.Problem:Speakerphone: As mentioned on the 1.st problem I couldnt hear the voice from the other side during calls, so I tried the speakerphone. Now this is very strange, Spekerphone during a call works fine with the speaker on the bottom of the phone, yet the other side can not hear my voice! :I That is really strange because as I mentioned before my microphone works fine with the third party apps, during normal calls, skype calls, etc.All of these problems since to be software related problems. My Iphone 4 was a gift to me, my uncle bought it from Qatar and its global warranty is unfortunately not valid in Turkey

Info:
iPhone 4, iOS 5.1