Cannot make or take phone calls/ whatsapp calls/audios - no audio, speaker icon on call is grey, siri can't hear me,

I have an iPhone 7 on 12.3.1

Just have seen a thread from a year with the same issue, no fix, no replies...so I copy paste:

I have an issue placing or taking calls. Either way the call appears to connect and the timer is running like the call is in progress. However the other end can't hear anything, and on my phone I can't hear anything. I would have liked to try to put it on speaker phone but the speaker icon is grayed out and its impossible since there is no other button to accomplish this. I am far way from my car inside a building, which is shut off, so I know the audio is not being redirected there (if it were it would say Mazda as the audio source).

Another issue is when I hold home button and actiate Siri, she cannot hear me. I can say anything here and it seems like siri is not picking up anything.

Audio from other sources work, such as a YouTube video for example. I tried rebooting the phone, which takes an excruciatingly long 10+ minutes on the apple logo to complete, but that sometimes fixes it for a call or two and then its back to broken again.

I do not appear to be getting any audio in my video recordings either. Any idea what I can do? Right now I have to have calls forwarded to my desk or home phone. That defeats the purpose of having the ability to make calls when out and about. I tried facebook calling yesterday and once it connected it kept saying call failed and booting me out. The only way I can communicate is by text message or facebook message.

Thanks