Software settings or settings on how to make a voice call on a machine or a Smartphone ( APPLE iPhone ) that has a SIM card with cellular connectivity to a 4G/4G LTE network from VERIZON

Source :  Internet 

1. From the Home screen, navigate: Settings > Cellular.
2. Ensure that Cellular Data is turned on.
3. Tap Cellular Data Options.
4. Tap Enable LTE.
5. Select Voice & Data to enable or disable.
    Enabled when a check mark is present.
    When checked, voice calls between compatible devices is carried over the 4G LTE data network.