Phone Microphone and Speaker not working.

I have an iPhone 4s. The power button was damaged so I replaced it locally as was in a hurry for a spare phone. Now the phone works almost perfectly.

When you make a call, you cannot hear anything and neither can anyone hear me. If I play music or games on speaker it works fine. All calls on the device are silent even if I plug in an earphone.

I tried resetting everything within the device, also tried resetting the firmware and also did the latest firmware update and still no luck.

Can someone please advise me on what is required as I would really like to get this fixed asap.

Thanks in advance.