Airtel — asking for a bill that we don't use

Address:

South Delhi, Delhi

dear sir/madam,
we have internet connection with a name of harish mahalwal . telephone no. is [protected] , account id 12492717 .we withdrawn our connection with them in march 2012 at that time they tell us to pay remaining rs 2700/- to clear balance and after that our connection will be cut by them so we paid to rohit mehni Representative of airtel rs2700/- cheque. cheque no. is 336184 bank of india, safdarjung enclave branch reciept no. 7584922 after that we get our closer no. from airtel i.e 701C09 .In march we take connection from mtnl. we are not using any service from airtel since then suddenly after some time we start getting call from airtel to pay pending amount for using internet usage from them .They tell us that we dont send a mail to them for closing of internet connection with them. we tell them on phone we got one confirmation no. from them i.e 701C09.
Now they are harrasing us by telling us to submit bill or come to court for penelty. We dont know what to do so we decided to submit a complaint here please help us .

regards

nitin