How to turn off VoLTE HD calls?

The closing method of vivo mobile phone VoLTE:

You can go to mobile phone settings-mobile network/dual card and mobile network-SIM card information and settings, and turn off VoLTE HD calls;

Some models:

1. Go to Settings-Mobile Network/Dual Card and Mobile Network/Phone, and turn off the VoLTE call;

2. Go to Settings-More Settings-About the status of mobile phone-SIM card, and turn off the VoLTE call.

3. Please contact the operator to turn off the VoLTE function of the SIM card.

Note: At present, when installing mobile, telecom and Unicom SIM cards on some models, the "VoLTE HD Call" option is hidden by default, and the VoLTE function is turned on by default, and no option is set. If you don't need to use this function, you can contact the operator to close the VoLTE service. If you want to experience the VoLTE function again, you can contact the operator to start the VoLTE service and resume using it.