Wrong Debit order for the third time in a row

This is the third time that I have been incorrectly debited for my tracker account. Tracker contacted me to say there was something wrong with the tracker in my vehicle and so they needed to come and change it free of charge. This was done and on the 1st October 2015 more than R 1000 was debited off my account when my premium is R140 a month. I queried this and they said they charged for the install incorrectly and so I waited the 7 days for my refund. The next month (1 November) again they debited over R200 from my account. After various complaints and no one getting back to me the amount was refunded. Now for the third time (1 December) my account was debited with R292 instead of my R140 debit order. This is so frustrating that you can get it wrong three times in a row. I do not want a debit order anymore as you are just debiting whatever you like from my account and I want my refund in my bank account today. I am not waiting seven days to get back money that tracker keeps on taking with no authority to do so. Highly dissatisfied.