Cartrack Nightmare

Due to the terms of my insurance co.I was forced by my insurance co to fit a cartrack unit. After approx 4 years I traded in the vehicle and had the unit swopped into the new car. After 8 months I changed insurers and notified Cartrack of my intention to cancel. Iwas informed that there was a cancellation fee of R2500 as per the contract I had signed. I informed Cartrack that if that was the case I would gladly pay and requested a copy of the contract. The nightmare began .Despite 6 emails and innumerable telephone calls and explanations I still have not received the supposedly valid contact. I am being continually hounded and harassed by telephone,sometimes as early as 07h15. My wife is also receiving calls and I am now being threatened with blacklisting. What can I do to resolve this? Should I be liable I am happy to pay . Show me your valid contract as per my recollection the contract expired in 2018