Netstar smart box

Hi am Khethiwe Mahlangu. I has a complain against Netstar contract I did not sign them. I had a car insurance with Dotsure they send me Netstar team to install a smart box on my vehicle Nissan Juke in 2020. I sell the car on the 28th of June 2022 and I call Dotsure to cancel insurance they told me to call Netstar which I did I even sent them emails but they sent me sms's claim that I owe them money for what? I was not supposed to sell the car because of their contract I was having a car insurance with Dotsure not them.