Why is my microphone not working at all?

Apple replaced my 7+ out of warranty due to the 11.3 issue; mine acted like the headphones were plugged in, even when they weren't. It's an issue affecting early build 7 and 7+es. If you go in they will run a diagnostic and it will fail the audio part of it. Bear in mind this issue has only just been recognized by Apple. I didn't even push them to get a replacement since I bought it used and figured I got a bum phone.

I would say it is most likley a problem with the audio IC on the logic board not making sufficent connection to the pads on the logic board. The latter would require microsoldering skills to replace that chip and put the nesecary jumper connections in place to make sure that this does not occour agian.

"I waited through 2 additional updates to be released and installed and still my iPhone 7 was not able to make calls or record voice memos.

I am an IT professional so I finally backed up to iTunes and backed up my device to the computer. I wiped the phone, restored backup to the phone and still had same issues.

Went to Apple and after 3 hours of them trying to solve it they replaced the phone but we had to fight them."

If hanging a new charger port doesn't fix it then it's an ic problem, this is common fault on iPhone 7.

"I just received a new iphone 7+

I called apple support and after long process of back and forth (it took a week), I received a new phone from an authorized service provider in Vietnam.

They said that it is a factory default problem because of the model month and year that it was manufactured. My phone was the first batch, September 2016.

I hope this helps."

i figured it out just now..don't spend money. it is a software problem.. download ios software from your itunes in pc . then restore it. but before you restore just backup any thing important files from your cp.. hope this help to you..