This happened to both my daughter’s and son in law’s iPhone 7 both of which were purchased in September of 2016. With my daughter’s she had a protection plan and her provider replaced it. For my son-in-laws I was advised it would be $315 for the Apple repair. Both were fine at night when they went to bed but in the morning after the forced update the microphone no longer worked. I took it to the Apple store and they advised me it was a hardware failure and that this wasn’t the first time that they had heard this but there was no authorized repair. It seems that there will end up being a class action suit on this eventually. Terrible that Apple has planned obsolescence built into their devices. Had I not already gotten a pretty decent deal on an XS Max, I’m pretty sure I’d never purchase another apple product. The factory reset did not resolve the issue. Apple gave me $175 for the iPhone 7 with the broken microphone.