Can't hear calls but they can hear me?

Whenever someone calls me, they sound muffled and the volume is very low. I've checked the volume and I've restarted it and I've cleaned the receiver as well, and nothing changed!

When I plugged in earphones, I could hear the other person again. Music playback and everything is fine. What else can I do?

It started shortly after I updated it. Perhaps something happened then?

I'd love some advice!