Incoming call does not work

[firefox-58]

Done it and restarted. Connection to the carrier is established. But no call was received. As noted before the screen flickers one time if the call arrives and nothing further happens
Calls DO WORK in UB-Touch, Manjaro-plasma-mobile and in Sailfish OS.

So this is no hardware or hardware related problem ????

I think that all OS equipped with PHOSH have the same problem here ???