

Try the Monitor of XXX device if the one selected by default doesn't work correctly.

You're hearing the audio on your phone but, also on your PC. You can prevent that by creating a virtual audio device on your PC.
These are the same instructions as the temporary method, but the virtual audio device will persist between reboots.
/etc/pulse/default.pa# Creates a device which your PC will output sound to.
# AudioRelay will be able to listen to it.
load-module module-null-sink sink_name=audiorelay-speakers sink_properties=device.description=AudioRelay-Speakers
pulseaudio -k to make PulseAudio reload the file.pactl load-module module-null-sink \
sink_name=audiorelay-speakers \
sink_properties=device.description=AudioRelay-Speakers
This creates a fake audio output device, it will be removed when your PC reboots. Or if you type pulseaudio -k in a terminal window.
sudo apt install pavucontrol
