iPhone 4 no sound or mic during calls

Hi all well as the title says I have an iPhone 4 that has no sound or microphone when making phone calls. To start off I should say I have a very small phone repair shop but this one has got me stumped. The phones bottom speaker works you can listen to music and the microphone works you can use voice control, the problem is only using the phone app! skype works. What has been done to date.

* Phone was brought in with this problem.

* The phone was first factory reset as it had other problems too like not getting 3G coverage (that was resolved with a restore)

* New ear speaker was installed.

* New Charging port flex with microphone installed.

* New Headphone jack flex installed (Thought it might have headphone problems causing it to lose sound but not even they work in a call !)

* New bottom speaker installed.

* With all new hardware we reset the phone to ios 7.0.6

I have tried several times to reset and I have changed the parts a few times still no luck not with normal phone function speaker phone or headphones plugged in do I get sound or microphone working during a call..... but skype and viber work!

anyways any ideas,fresh input or help is more than welcome.

Kind Regards Patrick