right! This is a temporary fix.They are able to completely control your WiFi radios remotely and it’s just a matter of time before they turn it back on again. You being paranoid about it is detrimental only to your own health because they have got it signed from you as a contract in which you have agreed to let them use “their FTTH assets” which are simply in your custody without your explicit consent in future.
The other options would be to arrange visit again and make them shut off those channels again and again.
2) DMZ via another dual band router and putting jio router in a faraday cage (and spend around 3k in these equipments!)
3)Switchback to local isp with rudimentary GPON box setup.
In your experience airtel or any other isp is also doing this hidden ssid business right now or plans to in near future like JIO unlicensed LTE plan?