Tata Docomo — PostPaid Connection billing for unused days

I took TATA DOCOMO Postpaid connection in Aug 2009 and used for a month and I was not satisfied with the service(signal reception) and I raised a cancellation request by end of august. They didn't cancel my connection even after following up many times. I had discarded the SIM card and was not using it also. But they called me back in Jan 2010 and said that I have amount due on my TATA DOCOMO Connection and asked me to pay it. I told them that I will settle the amount until the date the raised the cancellation request and asked them to provide me the bills. They agreed to do this but they haven't reverted back. Few days back I got notice from Tata Docomo saying that I have amount due to company for many days and that is why they suspended it. I have never come across such a bad customer service. Even after agreeing to settle the amount though I could have rejected to pay a penny, they sent notice as if I was wrong. Actually I need not pay a single Rupee to them because I have my refundable advance with them and I used the connection only for one month which will balance with the advance I paid. I want to file a complaint against Tata Docomo for its false claims and recklessness.