The mid-range Nokia 4.2 is getting dual VoLTE support in the latest update that comes with the July security patch.
Dual VoLTE support means that users of the phone will be able to connect to two 4G networks at the same time for both data and voice over LTE.
This update to the Nokia 4.2 includes the July 2019 Google security update and UI improvements.
How To Download Update
If you do not get an automatic prompt for the update, you can manually check for it by going to the phone Settings > About phone > System update.
We have the full specifications and features of the Nokia 4.2 HERE.
You can also read more on Dual SIM Dual VoLTE and why you need it.