Tikona Broadband - Claiming money even after disconnection

After having a very bad internet for * months I wrote Tikona to discontinue my service on ** Jan ****. Thereafter they are harassing me by making regular calls and sending me various amounts of bills and legal notices. One bill came for Rs ****.**, another Rs - ***.**, another Rs ***.**, another Rs. ***.** another Rs. ***.** another Rs ***.** and so on. After giving a complaint against them about * weeks ago Tikona people called me up and said all the pending bills were adjusted and there was nothing more to pay from my side. But unfortunately, they are again sending me to notice to pay pending bills. Their latest bill amount of Rs ***.** has no base because I have already paid all their bills for the period I have used their Internet. I also paid Rs **/- on ** January which their executive told me to pay as a final amount. Yesterday I got a legal notice from Tikona that I have to pay Rs ****/- in case I fail to return the modem to them. But the fact is that Tikona people have already collected their modem and all other accessories from my house about a week ago. After receiving their equipment they should ideally send me an acknowledgement of receipt but instead, they are sending me the legal notice to pay Rs **** towards the modem.