VoWiFi is a significant improvement over variable and weak mobile signals but it is not a panacea. Sometimes it works great and other times connections are as bad as ever, although IME a redial usually makes it better. It could be all or any of the device, the WiFi/router, the NBN connection, or vagaries of the SIM/telco. Anecdotally it seems some devices and services ‘struggle’ to switch between mobile and VoWiFi modes with resultant uneven experiences.
If one is beyond their WiFi coverage back to whatever signal (or lack thereof) you have in your location.
