Navigate: Apps icon > Settings > More > Advanced Calling.
Navigate: Settings > Connections > Advanced Calling > then tap Allow from the 'Advanced Calling' prompt to complete activation.
Tap Advanced Calling to turn on or off.
To continue, review the disclaimer then tap Activate.
Review the added and removed add-ons then tap Continue.
From the 'Congratulations! you now have Advanced Calling' section, tap OK.
Restart the device in 5 minutes to complete activation. Check for incompatible add-ons that must be removed in order for HD Voice to be activated.