Find the dual card and mobile network in the settings.
Make sure you use a mobile 4G card.
Because only 4G cards will have the VoLTE function.
It can be seen in both dual-card and mobile networks.
VoLTE HD calling options.
Turn on the option of VoLTE HD calling.
When you open it, you will see a VoLTE icon in the status bar of your mobile phone.
This means that VoLTE has been successfully turned on.
Sometimes even if the VoLTE function is turned on, the VoLTE icon will not be displayed in the status bar of the mobile phone.
This is because your current area has not covered mobile 4G, or the current signal is not good.