After that I uninstalled that app, however the message wouldn't go away.
I tried removing my phone from the Bluetooth devices and then re-pairing, removing my phone from the "Your Phone" app, deleting the app from my phone and setting everything up again, restarting my PC, but the message simply won't go away.
It seems to be stuck in the same state, no matter what I do. I can't think of anything else preventing the phone calls, because I haven't installed anything else since setting it up and it used to work fine before I installed the Bluetooth Audio Receiver. How can I get the app to recognize the new circumstances, which is the absence of conflicting apps ?