Consumer Redressal

I bought a Mts ultra wifi Dongle on 28th Feb, 2015.Mts gave me the connection on 5th march but it was not proper. I complained them many times regarding this but they never took any action against this.I have informed their customer to waver the billing amount as I faced so much problems but everyday They threatned me to pay an amount of Rs 1254(2 months rent). I have asked their pick up person to come and collect the rental of current month that is April'2015. Their customer care as well as the pick up person threatened me and my family members regarding the payment. Suddenly today I got a call Form a lady informing me that some one has raised a case in Delhi Court and she gave me another Number to know the details and asking me to visit Delhi court.They are continuously harassing me and my family mentally on daily basis. What Should I do ? Should I pay the amount Which I have not use ? Please Help