Rick,
I just read the press release from 2015.
Than, they say "working in Switzerland....other countries in a later stage".
You can only enable or disable WiFi calling on your iPhone. Nothing else.
If that doesn't work, than could be that WiFi Calling is not available for Swisscom customer abroad.
But I don't know for sure.
Please call the help desk 0800 800 800 and ask them directly.
Sincerly