WRONG DEBIT BY NETSTAR

Please help

I bought a car that had a Netstar tracker, that was paid in full by Dealership and I had to take an Insurance with Dotsure when I cancelled Dotsure I was told that I will have to pay Nestar for 3 years which I did

Now Netstar is deducting the money from my account even though I have paid them in full and cancelled the contracts

They told me that I have to pay for cancellations of both Trackers. What upsad me the most is that the deducted money for the new box that was never installed in my car before talking to me or asking me if am renewing the contract.

When I reversed the money they continue to debit my account, and i reversed it I had to send emails everyday to recieve cancellation letters,

Yesterday they send me an invoice I don't even understand how they got to the amount they are expecting me to pay, when I tried to reply back my emails are blocked