Having problems with wifi calling. since the update today I have lost wifi calling from A7 2018. Been onto Samsung and told to leave message on here as they could not help. May need a new update to solve the problem.
I had an update on my s20 yesterday. I too lost wifi calling so I rebooted my phone and it came back, tried wifi calling and it worked great . Don't know if this will work for you but it's worth a try.