BSNL — Landline connection is not disconnected even after gave the letter

Hi I was using BSNL Landline. But the service is not good in my resident area. So I asked them to disconnect the line. we intimated them lot of time but they haven't disconnected the line. But bill is still coming. Now they called and asked me to pay the bill. I told them i disconnected the line. They are not responding properly. My Landline number is[protected]. City : Coimbatore Area : Telungupalayam We gave lot of letters to the Raja Street BSNL office. Still they area not Responding.