cheating and selling connection

Location/place: Bangalore

Name of company/service: Tikona

I had got a Tikona broadband connection on November 2011 because the Tikona salesperson told me that a limited offer was going on and if I take a connection quickly before the offer expires, I will get no bills for the first 2 months. I had heard of salespeople fooling customers and hence when the Tikona salesperson came home to get the subscription form filled and get the initial payment, I got him to sign on paper that there will be no bills for the first 2 months. I clearly told him that it was only for this offer that I was taking the connection. After some days however I got a bill from Tikona. I mailed Tikona customer care about the offer and to correct the bill. They later reply that there is no such offer. I told them that it was promised by the Tikona salesperson and if it is not corrected I will disconnect the connection. By this time I had got the second bill also and when the Tikona Billing did not agree to give me what was promised initially and told me to pay or else face disconnection, I disconnected the connection. I continued to receive bills for couple of months and when I called and informed the case, it stopped. Then mid of 2012, there was a person from the collection agency at my house. When I showed him the signed paper of the Tikona representative and explained how the Tikona representative had cheated me, he left. Now about a few weeks back I am again getting mails from “Tikona Legal Collections” asking me to pay. I am really annoyed with this. How many times should I keep explaining them what happened? I had scanned and sent the signed paper to the Tikona customer care, Tikona collection agency and now the Tikona legal collection. In spite of this, for the second time, Tikona legal collection has sent a mail last week asking for payment. If somebody has to pay, it has to be Tikona for cheating and selling a connection and for the agony for pestering and threatening. Is this the way to do business? Luckily I have the sign and the employee ID of the Tikona representative but still lose peace of mind everytime someone new from Tikona calls regarding this. How long should i keep explaining?