Unauthorized debit amaount

I have am a Cartrack client and in 2019 Cartrack stopped debiting my account for some reason and I called them to fix the issue and then 2 months later they stopped debiting my account again and debited me as and when they felt like it. Cartrack has been calling me to make payment arrangements which I gladly made with them and for the life of me I can't understand why then would Cartrack debit me a ridiculous amount which was not part of the payment arrangement and this is the 3rd time this is happening. I am going to reverse this amount that was debited and I will continue to do so up until Cartrack sticks to our payment arrangement plan which I got into because they stopped debiting my account for what God knows why. I am fed up with Cartrack and I would like to cancel this contract with Cartrack, I will not take this harassment from you going forward.