hey guys just to update you all i got Airtel Volte on my 6z.
Airtel Volte is not officially supported on 6z yet but there is a way around.
You need a device that supports Airtel Volte i had one such device.
Put your 4g sim airtel sim in that device and you should get Volte( keep it for atleast 1hr in that device if not getting volte)
Remove sim and put it in 6z and voila! Volte is there in 6z. Below is the screenshot