The TA-1012 variant of Nokia 8 is certified for the E.U., South Africa, Australia & NZ and Mexico. It is VoLTE and VoWiFi capable out of the box.
Settings > Network & Internet > Mobile network v Advanced = toggle on 'Enhanced 4G LTE Mode' and set the 'Preferred network type' to 4G.
Does this help?
I have never had that option but VoLTE and VoWiFi still work.
Image shows with and without Wi-Fi so the voice method switches.