Airtel — Airtel modem picked and was not updated

Hello, we have had some issues with the wifi connectivity of Airtel in the month of Feb. we wanted to remove the connection and hence contacted 121. After that the customer care executive asked for a day’s time to find a resolution to the connection issue and send a technician after that. On 22nd February a technician came to our house and we submitted the router to him and we were assured that the connection will be discontinued. Post that in March we received the bill and it had the excess amount. After that we contacted the customer care and they mentioned that the connection is still active and not deactivated.
We then gave them the details of the technician who came to pick the router. They have not yet looked into the matter. I have received multiple calls from different executives and still no resolution have been provided. I am seeking your help to resolve this issue because the modem was picked on 22nd February and still the bill is being generated. And no resolution is provided till now. We are the only one connecting airtel and still they have not adjusted the bill amount.