Wifi calling not working

Team,

I am using iphone 6 32 gb model India location. I recently ported my number to jio from airtel.

After porting my number to my surprise , when I went under option mobile data in settings , under my network name jio i was able to see wifi calling option and i enabled the same. I was able to make and receive calls over the jio wifi without any problem for almost one week. However 2-3 days back suddenly the wifi calling option is not coming and i am unable to switch on wifi calling and make or receive calls over wifi. I have checked all my settings, done restart of my phone many times however still issue is same.

I know that iphone 6 is not showing under supported model for wifi calling, but then how come i was able to see that option when i ported to jio and able to use the same. But after one week the option just disappeared on its own. When i contacted jio support they asked me to contact apple care.

Request your kind assistance for the same.

Thanks,

Nikhil Dhawan