The "VoLTE HD Call" function belongs to the business scope of operators (China Mobile, China Unicom and China Telecom). To know the setting of "VoLTE HD Call" function, please call the SIM card operator.

Tips:

After the "VoLTE HD Call" function is enabled by the operator and successfully registered, the "VoLTE HD Call" function is enabled on the mobile phone, and the word "HD" will be displayed in the status bar of the mobile phone. Cancel the HD calling service, and the HD disappears.

Take the model of ColorOS 12. 1 system as an example:

Go to mobile phone settings-notification and status bar-status bar-status bar icon-HD call, and close to cancel HD display.