Sounds like (hah) you have audio but the wrong device(s) is used for the call. There are other similar threads that may have clues (for instance) - one of them got solved because they had conflict with Dino. For more troubleshooting, make a call and look/test the sound settings (can you get something to work - like if you connect headset. You could also install pavucontrol to see if that shows other options. You could also try resetting the sound profiles: rm .config/pulse/*, then reinstalling pulseaudio to getting them back with sudo apt reinstall pulseaudio, and starting the service just for good measure with systemctl --user start pulseaudio.