As written in previous post I upgraded to 5G phone. As per Welcome offer I am getting unlimited 5G data from Jio.
When 5G network is available (it is available most of the time in my area) there is 5G icon on top panel.
When I call someone or there is incoming call the 5G icon vanishes and the call goes over 4G LTE network.
After searching on net for this issue I discovered that my phone is not having VoNR or Vo5G calling feature. You can read about what is VoNR or Vo5G on the following website:
What is Vo5G or VoNR? Everything you need to know
Vo5g is available on Jio since it is SA (Standalone) network but Airtel has no plans to launch SA network.
I conclude that 5G has arrived in India only for data and calling will take place on 4G LTE network even on so called 5G phones.