Hi
robdevilXIThank you for your asking. To activate VoLTE or VoWiFi, please refer to the check point below:
1. Which carrier are you using? Please check with your carrier, does your SIM card support VoLTE or VoWiFi?
2. Please check if you have open the VoLTE or VoWiFi
VoLTE: Settings>Network & internet>Mobile network>turn on "VoLTE">Preferred network type>2G/3G/4G
VoWiFi: Settings>Network & internet>Call>Wi-Fi calling>turn on
If you have any further queries, please do not hesitate to contact me.