Tata broadband charging for period after closure of connection

Recently I have received a notice to pay Rs 664 in a court to tata broad band as pending due by 30th June 2013.
I called Tata boradband customer care multiple times in last two days to explain the wrong bill over phone. They agreed to my arguments and told me that someone senior from Tata broadband will contact me. But it did not happen.

Facts:
Connection start date: 31-July-2012
Connection end request date: 24- Dec-2012 (Tata boradband accepted my request to terminate and confirmed through mail on 24-Dec-2012)
Disconnection from my end: 24- Dec-2012 (stopped using the connection and disconnected equipment)
Total usage period (connection period): Less than 5 months
Initial Payment: 4 months advance rental payment (Rs 3595)
Second payment on 15-Nov-2012: Rs 25
Third payment on 15-Dec-2012: Rs 898 (one month's rental)
Total payment: More than 5 months rental

I should be receiving some refund from Tata broadband but to my surprise they are charging me for January 2013 rental erroneously and asking me to pay them Rs 664.
Without any follow up or mails from Tata broadband, suddenly I got court (LOKNAYALAY NOTICE) notice to make payement.
Please suggest how to handle this. I will appreciate if consumer court takes this up to save me from this kind of harresment.

Thanks,
Sanjay