Bill includes amount for services stopped

I had availed airtel 3G services. on 5th of may i requested them to stop the services. I rceived a confrmation that the services have been stopped on the same day. But when i received the Bill for May 2013 The bill included the Intenet charges for may 6th 2013. When the services are stopped how 5.5 2013 how can they charge for the services on 6th of may 2013. they contend that i have browses internet on 6th may 2013 through their 3g card. But if the services are stopped on 5th how can they allow me on 6th. I had also land line intenet also of Airtel at home which was used to browse intenet through wifi. They are charging based on the devise tracking not on the bsis of sim card. i had lodged a complaint in this regard they called on me asked me pay the bill instead of resolving the complaint. In june i told them to stop the services. I still continue receive the bill for all the months upto aug 2013. I have clearly told them that i am ready to pay the the Bill for may 2013 minus of internet charges plus of june 2013( minus of intenet chrges), as i am not using the their services ever since the dispute. Their complaint resolution mechanism is also not good, as we have to go through the call centre mechanism. there is no single person who can resolve the dispute. They have also sent a person on 4.10.2013 marking me as a defaulter instead of solving the problem. My reputation is tarnished.
Please help me in resolving the complaint and for the mental agony a compensation of Rs50000/- be awarded. The airtel company is always cheating the people.