How do I choose between VoLTE or VoWifi?

If your device supports both VoLTE and VoWifi, you can activate both options. In fact, your device will do the rest, choosing for you which connection works best. It will always give priority to mobile data. If your 4G connection is too weak, your device will use the WiFi signal. Is your connection getting better again? Then you call again via 4G.