S6 Edge Plus Verizon..

[S7 Edge]

Hello, I'm using G928V in India, unable to use this phone with the Indian Jio SIMCARD.. I can use data but cannot call.. I cannot locate the VoLTE option in the phone setting. Also, i bought the phone 4mnths ago, haven't had a single OTA update... I just dont know what to do!! Will flashing an Indian firmware resolve the issue?? Is there something I need to use to enable the VoLTE option.. PS- Currently phone is not rooted.