Billed for a Tracker not Installed on vehicle

I purchased a new vehicle in Feb/March 2015. I called AltechNetstar and requested cancellation of my old Tracker contract on a Toyota Auris. I had a month-to-month contract. I requested installation of a new Tracker device. I was advised to approach a service provider nearest to the dealer. My dealer was Hatfield VW Braamfontein. I contacted Elsie Dlamini at Digifleet, a company located at Lyndhurst Johannesburg and informed her that I wanted to install a device. I informed her where the vehicle was and the name of dealership. Due to a dispute between myself and the dealer on the specs of the vehicle, I called Elsie and informed her to hold off on the fitting of the Tracker device, as I was looking for an alternative vehicle, which I eventually got at another VW dealership. Despite this, Elsie contacted Dean at Hatfield VW Braamfontein and proceeded to install the device. I received a bill for a tracking device which I neither own nor have in my vehicle. I have spoken to Rose Bila and Sifiso Nkosi who have both promised to escalate my query, to date I have no joy. Instead I have been handed over to Nu-Debt Management. I am being harassed day and night.