Ok, I don't want to be Debbie Downer, but I don't see it mentioned, so be aware that wifi calling is only as good as the wifi network you are on. If your calls are continuously getting dropped then the wifi you are on is either (1) saturated with traffic or (2) not properly configured to handle wifi calling.
For example, with Tmobile I had to make sure a couple of ports were opened in my router (which they weren't). Once I made the change wifi calling worked great.