Iphone won't call or record voice memos etc

Hi - I have no idea what is going on with my iphone 7 plus - it seems to be functional in every way except that it won’t let me make calls or record audio.

I can call out on the telephone but people don’t hear me and I don’t hear them.

I can’t even call out via apps like whatsapp or messenger, it won’t let me dial.

The same is true of voice notes, won’t even allow me to start recording.

Videos will record but no sound.

If I attach a headset it doesnt change anything.

If, however, I connect to a speaker through bluetooth it DOES let me record a voice note, even though the speaker has no mic.

I feel it must be a software problem since obviously the mic and the top speaker aren’t working. but I have now reset the whole phone and erased all settings and the problem is the same.

I’m very far out of warranty so does anyone have any ideas before i simply have to buy a new one?

Any thoughts very very welcome, and will be gratefully received