iPhone 7 microphone not working

Hi,

my iPhone 7 is now useless as a phone as when I make or receive a call there is no sound. I recently downloaded IOS 13.3.1 and the next day the phone feature stopped working. Since then I have had a frustrating experience getting the run around from Apple and their authorised agent in Ireland. Any suggestions how to fix. I’ve checked the microphone vents and restored factory settings etc all to no avail. Btw seems to be loads of posts on this issue, anyone what it takes for Apple to do the right thing and provide a repair or replacement program? Thanks in advance