Tata Photon Plus

I had purchased a Tata Photon Plus in 2013 for Rs.5000 for 6 months. At the end of 6 months in December 2013, I received a call from Tata Photon personnel reminding me that my 6 months period is about to be over and whether I would like to continue with the current plan or not. I said I would like to continue with the current plan. Few days later I again received a call from a Tata Photon personnel asking me to buy a new Photon Plus connection on the 6 months plan as it would be cheaper. I agreed and they sent a salesman to my house to collect the money and give me the device. In the meantime my 6 months period was over and I had used my previous Photon Plus device for around a month. At the time of selling me the new device the salesman told me that my old device would be deactivated as soon the new device is activated. I believed him. Around March 2014 I receive a call from a Tata Photon personnel that I have to pay Rs. 4000 as my dues for the previous device. I had used the previous device for less than a month and my dues would be Rs. 950 + tax for one month. These guys are demanding 4 times that amount. They demand that the connection was not deactivated and had been going on for 4 months. I agree to pay for 1 month that I used but they agreed to reduce the amount to Rs.2300 (I have no idea how they can reduce the bill amount!). I paid that amount. I got a new device on June 2014 this year from the same person who sold me the previous device as the previous device had been deactivated after 6 months was over. After around 10 days the new device stopped working again and after numerous calls to the person who sold me the device they say that I have to an amount of Rs.1700 from my previous connection. I have paid Rs. 5100 for the new device and now they have blocked it saying that if I don’t pay up Rs.1700 the device will be blocked. Also to be noted is that I have never received an email or paper bill regarding my outstanding amount and only calls have been made and unethical measures have been taken to extract money from me. Please help.