When activating volte via text message from a telecom card, it prompts that the index does not exist. What is going on?

When activating volte via text message from a telecommunications card, the prompt that the index does not exist is due to improper operation. The correct steps are as follows.

1. First, open the phone’s main menu option and select the settings option on the right.

2. In the displayed list, click to enter the dual SIM and network menu.

3. For mobile phones that support dual SIM cards, click to select Set Mobile Card to enter the setting interface.

4. Next, scroll down to find the volte HD call option and enable the corresponding function.