Cartrack - would rather they ***** my car then use them ever again

What a horrible experience trying to cancel this contract. I have been paying them for more than 12 years. When I sold my car recently, I sent a cancellation mail to them. Within 2 hours they phone me and threaten me with a cancellation penalty of R2600 or something ridiculous. I cancelled the debit order for R242 with my bank, only to find that they loaded a new debit order amount the next month, and increased the amount to R300 without notifying me why they are even charging me more than before, for something that I cancelled and is no longer in use. VERY *********! Not to mention the threatening emails, whatsapps, phone calls. I will NEVER use them again, period, and will not recommend them to anyone. Poor customer service from such a big company, you have not been in business since yesterday, would have expected better from you. Or is it that you just don't care?? and you get away with it, cause some people are too scared to challenge your actions? Show me the contract I signed 12 years ago, that stated that I would be liable for a R2600 cancellation fee, I am waiting.