Airtel — Security deposit refund for DTH account # [protected]-001

I have not received refund of my security deposit form Airtel after I requested cancellation of my Airtel Black plan. They have also collected the wifi router and set-top box from the location. After collecting these items they are denying refund saying that service was not active for 12 months. I had service active for 11 months and had to cancel it and Airtel does not provide service on the location I am living currently. I request airtel team to kindly look into this matter and process the refund.
DTH account # [protected]-001