I've been using my s20 ultra for some time now and I haven't had this issue. I am pretty sure I turned off the notification for wifi calling because it constantly gave me the notification. However, both me and m a family member who owns an a71 have had this notification constantly pop up without a way to disable it. We both use tmobile if that helps anything. It's infuriating that I have to disable wifi calling if I don't want this notification now, I would like to, once again, just disable the notification.