How does Unicom open the VOLTE function through SMS?

The use of VoLTE in China Unicom improves the call quality and reduces the drop-off rate, which brings you the most direct feeling, that is, higher quality and more natural voice and video call effect, so that you can experience the service of connecting to the Internet without delay, and there will be no network switching or drop-off when making or answering calls. Edit the short message "DGVOLTE" and send it to 100 10. Just confirm y.