Tikona Broadband - Internet not disconnecting

Tikona Internet was frequently disconnecting for more than * months and hence I requested them to disconnect my service on ** Jan **** with immediate effect and subsequently reminded on ** Jan ****. Instead of taking back their adapter they keep on sending me bills and calling me every day for additional payments. My Tikona Internet was frequently disconnecting since Sept ****. Every time I had to give them complain and wait for their people to restore my connection. Gradually I realized that the Internet was of no use and I was simply wasting my time in giving complaints and talking to their people. Finally, on ** Jan ****, I requested them to disconnect my service with immediate effect.
After this, they requested to observe the Internet for *-* days without paying any extra money. I observed the internet for * days and there was *-* days downtime during those * days. So on ** Jan I told them that I had already disconnected their cable and requested them again to discontinue my service with immediate effect.
While my monthly plan is ***/- rs and I had paid all their previous bills, to my surprise they sent me a bill of ****/-. When I spoke to their helpline they (Vaishali) said it was a mistake in the bill and I had to pay just ** rs to settle the final account. Accordingly, I paid ** rs ** January. But soon after they said I had to pay ***+ rs more as I was using their Internet. This was ridiculous as how could I use their internet while the cable is disconnected and thrown. Since then they have been sending me bills of different amount and calling me on daily basis asking for money. I told them to first send me the disconnection letter and then ask for any unsettled amount. But instead of giving a disconnection letter they are sending me emails charging me on Per GB basis (while there is no usage at all) and calling me every day for the various amount of money. Sometimes Rs ***+ and sometimes Rs ***+ and keep on harassing me.