Faulty units, ********* processes, harrassing

I've had a tracking unit installed by Cartrack for the 6 years, however this was part of my car insurance package and the insurance company has the contract with Cartrack and pays them directly. (I have never made any payments to cartrack). Recently the unit stopped functioning. I noticed this via my app. When I called cartrack, they required a fee to come take a look.

I decided that this principal is Ludacris considering that they should ensure that the until is working at their time and costs, so that they can uphold their service level agreement, considering that's what they are being paid for.

Anyway, I then asked them to cancel the services and I also immediately informed my insurance company to cancel the service based on whatever contract they had, to which I received confirmation that it was actioned.

Now I keep getting sms's from Cartrack for further payments, stating final letter of demand etc. It's becoming harassing. Poor service. I do not have any contract or payment history with cartrack. Stop harrassing me for payment.