I used Virgin text message help (07533016422) Whilst it took ages I got the solution.
1) My SIM settings (as you said) had to be setup - I now have "WiFiCall" shown on my phone
2) I can receive and make calls with WiFi Calling (i did not realise you could receive them). This is great as I have a poor signal at home, but now I don't even need a signal. Basically the default is WiFi and cellular does not kick in until no wifi signal.