Policy Cancelled

I had a policy with Dotsure they told me their policy includes Netstar car tracker on their amount, now I cancelled Dotsure they send me cancelation letter to confirm it in July now Netstar is debiting my account without any mandate and what ****es me of is that now they threatening with Lawyers massages also telling me that it will affect my credit record they say I am owing them R656.70. I never communicated or app**** with them directly so whatever agreement they had with Dotsure they must sort it out.