If ever encountered this try to update the device flash firmware first before proceeding to hardware troubleshooting.
If the flash firmware is successfully been done and nothing happens: The solution below will you which particular circuit components on Nokia C3 PCB board that needs to be check and replace if found damaged.
Nokia C3 Microphone Failure Hardware Repair Solution
You may need to check this components first and then replaced if found damaged.
If all of these components seems all perfectly working, you may then proceed to replace the microphone module.
There is an instances that you may need to rework the JUNO IC after ensuring that of those corresponding components including the microphone module seems all working but still the problem exist.