Stop Debiting My Account

On the 20th May 2015, Tracker ran a debit order through my bank account even though i have never been and still continue NOT TO BE THEIR CLIENT. on the 28th May i contacted their call centre and was put through to Steven Malepe, Credit Controller Finance, to inform them they need to remove my banking details from their system as i have NEVER been involved with Tracker. I had to take time out from my own employer to stand in the branch of my bank and get a letter confirming my banking details which i sent to him by email [Email Removed] . Upon not receiving confirmation that my email was received, i called Tracker back and spoke to his Team Leader, Chipiwa Chitsa, whom i also sent an email with confirmation of my banking details [Email Removed] At least Steven had the decency to come back and stated that my query had been escalated to the relevant department. I guess that's where it ended as to my utter shock and horror,Tracker have once again today debited my account, this time for R571.10, with the same Reference as the last time AD***. What must i do for Tracker to STOP debiting my account?