Currently Being ModeratedRe: My iphone 4 mic when making calls doesnt work, if i use earphones with built in mic will this work?Jan 20, 2013 9:06 AM (in response to rk8479)
Try making a voice memo to see if the microphone has failed. If voice memo doesn't work I would do a back up then restore as new to replace the software and rule that out.
If the restore did not fix it then you have a hardware failure with the mic. Call AppleCare to have them fix it