Intermittent wifi calling on two different iPhones
I've got real problems with wifi calling on my iPhone 12 mini and my wife's iPhone SE.
It starts and stops a dozen times a day - completely at random. I've tried everything I can think of - turning wifi calling off and on again, resetting the network settings, rebooting the phone, switching airplane mode on and off, even going back to factory settings and restoring the phone. Finally I even got my broadband company, Vodafone, to change the router. Nothing works.
Sometimes both phones have or don't have wifi calling but sometimes the SE will have it and the iPhone 12 will not. But I was lucky enough on one occasion to have both iPhones in front of me at a time when they had no wifi calling and then suddenly both got it again simultaneously, which makes me think we can rule out an iPhone fault.
There's obviously some kind of clash between the iPhones, Vodafone's broadband service and the mobile phone provider, Virginmobile. But days - literally - talking to them have not provided a solution.
Before I ditch Vodafone as the broadband provider to see if that works, has anybody else had a problem like this and found a solution?
iPhone 12 mini