I own a J3 2017.
It has always been able to use voLTE.
Recently, it’s microphone broke and I replaced it with an identical model.
Same software version, identical hardware.
I moved my SIM from the old phone to the new, but the new one does not have a voLTE option.
If I put my SIM back into the old phone, the voLTE option is still there.
The only difference I could find between the two phones was in the iD Internet access point, under the Access Point Names menu.
The new phone (voLTE unavailable) has all the options unlocked, and I can edit them.
The old phone (voLTE available) has all the options greyed out and I can edit nothing.
If someone could explain to me how to get voLTE enabled on my replacement phone, I would be grateful.
