Cartrack contract won't cancel when you sell your vehicle

I was insuring my motorbike in December 2023 and was required to install a tracking device. I signed up with Cartrack for R200 per month and they came and installed the unit at my home. A few months ago I reported that it wasn't working, they said they needed R600 to come and check it, despite me paying them R200 per month. I contacted the insurance company to report that the tracker wasn't working, and found out that the bike was actually insured without a tracker, so I went back to Cartrack to cancel my contract. They said I would have to pay about R4000 to cancel as the contract had not matured. I am now selling the bike and contacted Cartrack to remove the unit and they say they still want R4000 cancellation fee because the contract has not matured, even though I won't own a bike to put the unit in. I never wanted the thing in the first place, but to require someone to pay for something they can't use is ridiculous. Watch out for these guys, regardless of how long you require their services they tie you into a long term contract that you can't escape