Debit as they please!

So I've temporarily cancelled my tracker service with Ctrack. They quoted me on a cancellation fee which amounted to approx R600. I then told them to dust it the past month. When the debit order came through it was R999 deduction. I then called the customer care and they told me they will escalate this with finance department. Three days have passed now with no assistance whatsoever. No one has came back to me.