Airtel — repeated threatening calls despite request for discontinuation of data card

I was using airtel data card number [protected]. On 20th july it stopped working. Since it had given me problems earlier also, i decided to discontinue. I called airtel customer care on 21st july and requested to discontinue the service which the call centre person confirmed me that the connection will be disconnected effective 22nd july. After about 15 days later i got a call where i was told that i have to pay the bill, when i questioned them that i have cleared all dues till 22nd july then which am i supposed to pay?? He did not clarify.
After this i started getting calls from airtel call centre where they were demanding money and using threatening language and abusing me
Now airtel staff is giving me threatening calls very frequently. I can file a criminal against airtel as they are using unfair practices to extract money and it amounts to mental torture. Please see to it that this is stopped immediately. Negligence of airtel staff cannot be covered up by such means.
Please ensure such calls are not repeated and appropriate action taken against airtel
Thanking you
Neelam kaur
[protected]