The phone is a Galaxy A13 with a Virgin sim card and Virgin broadband.
I have four wireless access points in the house which connect strongly to the phone depending on my location. They are all connected to the same Virgin broadband router. Sometimes the wifi calling option is shown on the phone menu - sometimes it is not. One day it will be there, and another day it’s disappeared. Sometimes there is a message to the effect ‘ the sim card data is being refreshed’. This is always bad news. After this message they either don’t work at all or some do. There is no predictable pattern.