Reliance Communications — extra bill paid no refund but still getting bill

I had paid outstanding amount of rs 2800 for disconnection though my bill for month of november 2017 was rs 1800. Instead of refunding rs 1000, they have come up with new outstanding bill of rs 3117. My netconnect service was disconnected in the month of october 2017 itself. I hope reliance refunds rs 1000 instead. Please resolve this issue as i had paid more than the disconnection amount in month of november 2017.