No Wifi-Call eventhough the option is set


Sep 18, 2021

I have Wifi-Call enabled and my provider also supports it. However it's doing always VoLTE. I tried the Flight Mode, enabled the Wifi and tried calling, but no call is possible then. What can I do?
I tried the modem commands like *#*#86583#*#* to enable Wifi Calling, but I always get a failure "Not finished as this is not the default dialer...".
Yes, I have an alternative Dialer "DW Contacts" installed, but trying that with the Stock Phone app. How can I make that default temporarilly in order to try the command again?