Payment not Setteled

For my credit card my total outstanding was 26931.06 in Jul-Aug Statement, when i got a call from collection department I asked them for final settlement for hole outstanding with Rs. 12000.00 & made payment of Rs. 12000.00 on 23/08/08 for the same thru Receipt No. 0364069 to Gurusai Enterprises, but when I have received a statement for Aug-Sep & it is showing Rs. 15688.91 outstanding & still I have not Received my Letter for Final Settlement, So many times I have contact to Customer Care & Collection Department but I am not getting proper response.

Please reply back with Proper solution.