Poor service I wouldn’t recommend

I bought a car and it was fitted with the Netstar tracking device. After a year I decided to trade the car in before finalising the deal with the dealership I called Netstar several times to notify them that I was Planning on trading in the car so I want to cancel the tracking device then once I have received my new car I would like for them to fit the new car. All was well and in July I paid the monthly contribution for the new car. Now in august they billed me for two cars. From the usual R207 to R812, I’ve been calling to get someone to explain to me how the amount increased to R812 no one is giving me a tangible response.I’ve been calling to ask them to listen to the recording calls however no one has given my feedback since.