Iphone 7s... calls stopped working (connects, but unable to hear or be heard

Good afternoon.

Long time iPhone user. New problem with my iPhone 7s.

I call someone, the call connects, I cannot hear them they cannot hear me. Same issue if they call me. I answer, I cannot hear them they cannot hear me. The call is "active" - the seconds indicate that they are connected.

Everything else works on the phone - texting, sound, etc. Just that the phone is no longer a phone.

I tried to work with ATT - I even bought a new sim card ($5) through them.

They stated it is likely due to the phone - so they told me to take it in to Apple.

Before I do that, thought I'd inquire here.

Anyone suggest anything?

Thanks in advance.