Note: The following information applies to the devices IS330.x, IS530.x, IS540.x and IS930.x. Depending on the device and operating system, the position and name of the buttons may vary. 

With this small steps you can enable VoLTE for your device.

The following example describes the procedure using the IS540.1 with Android 12. 

 Open <Settings>

Select <Network & Internet>

Select <MOBILE network>

Enable <VoLTE>

NOTE: Your provider must authorise this option for your SIM card. If it is not activated by the provider itself, you may not be able to make these settings.