[Closed] Odd android phone calling problem

Ok, got s Samsung S8 I bought off here a couple of years back. Been ace and not keen to change. But recently, when making phone calls, it's developed an echo for the person I'm phoning, or the call is dropping in and out for me. Seems to happen now on most calls, irrespective if mobile or landline, my signal strength. Works fine on speakerphone and headphones. Sometimes switching speakerphone on off during the call resolves it.

I've tried with the case off. Checking both mics for dust/blockage, safe mode, factory reset and all 'sound' settings. It seems to crop up a fair bit on Google and switching off 'noise reduction' can help, but I don't think I have that option.

I need to make calls, and really don't want to have to buy a new phone.

Help!