SOLVED
I have a simple fix that got the mic working again on my iPhone 7 and 8, but as expected, it’ll cost you some time and money to get around Apple’s buggy IOS 13 software. The cost isn’t too bad though, at under 10 bucks per
phone.
I got hit with this latest “Apple surprise” while on a road trip when the mic on my wired earbuds quit working when I tried to make a call. I suspected software settings, but I had the same problem on both phones with different sets of earbuds and multiple settings. This was a hardship for me, since I am slightly hearing impaired from too many loud motorcycles, rock concerts and shotguns back in the 70’s. (I had a LOT of fun back then - still do.)
When I got home, to my surprise everything worked fine on the earbuds and headsets there. That’s when I noticed that the working units at home had the Genuine Apple Lightning to Headphone Adapter jacks on them, while both sets of non-working earbuds in my road bag had aftermarket adapters.
A quick trip to the ATT store for more Genuine Apple adapters and the problem was solved.
It’s impossible to tell if the problem was caused by poor software or a brilliantly executed evil Apple marketing plan, but in my mind, this battle ended with a tie. I got to keep my non-Apple earbuds and headsets but Apple forced me to buy more of their adapters.
Good luck to all and I hope this works for you.