How to open a high-definition phone?

The way to turn on the HD phone is as follows:

Tools: vivos 12, OriginOS 1. 17.2, mobile phone settings.

1, first open the phone settings.

2. after opening, click ISM card and traffic management.

3. Click the SIM card you want to set up.

4. Find the VoLTE HD calling function.

5. Finally, turn on the VoLTE HD calling function switch.