Dear Friend, for your information:
One of the major advantages of VoLTE and VoWIFI technology is HD video calling. If both parties support either VoLTE or VoWIFI, then the call clarity will be in high-definition, thanks to the higher data bandwidth. Similarly, these technologies can also be used to make native video calls as well.
Do note that, both VoWIFI and VoLTE are data-only networks, where both voice and video are sent as data from one point to another. In another way, network providers are using the characteristics of LTE to initiate calls over WIFI, hence VoWIFI.
When a smartphone capable of VoWIFI is connected to a WiFi network, one will be able to make a voice or video calls. This means, even if there is no mobile network, one will be able to make and take calls just like a Skype or even a Whatsapp call.
A Skype call or a WhatsApp call will use more data compared to a VoWIFI calling. Similarly, one can call to a landline or a feature phone using a VoWIFI technology, whereas the third-party app-based voice call does not work that way.
Do note that, to make or receive voice calls, the network uses the data from WiFi and not from the mobile network. This means, whenever your phone is connected to a Wi-Fi network, the phone will be in the network.
https://forum.huawei.com/enterprise/en/volte-vs-vowifi/thread/607800-100303
Thanks!