Airtel Broadband — Connection cancelled but bill generated

Address: Bangalore, Karnataka

Hi,

I have raised a request for my airtel broadband connection in the month of may. They hav cancelled in july. i have asked for the full and final settlement and paid in the month of july. In august they have again generated a bill and sent to me. They are causing inconvenience to me by calling on every alternative days. I have mailed the concerned teams many times. Inspite of this there is no update in there system?
Now they are saying that they will issue legal notice.

Please let me know what can i do in this case?