Blacklisting **** from Netstar

Well I bought a car from a dealership and informed them that I will use my own tracker from Discovery. Its been 3 months now Netstar hounding me for payment. Today they sent me an sms saying they will blacklist me yet I have no relationship with them. I did tell the salesman who said netstar would come retrieve it as i do not want to have to trackers on my car. When I called the call center with the reference ***4 The agent named Rajen wanted to get my personal details and I could not give them because as far as I am concerned I have no relation with them. I am even not sure if this is a **** that they use to get personal information and get into your bank account because they use same verification used by the banks. The agent didnt even want to check why they still billed a person they dont have a relation with. Insisted on me giving him personal information I am entitled not to give.