8ta Debiting bank account without permission

I have signed up with Telkom Mobile (8ta) on a contract that cost me around R565 per month with a R100 limit. All went well for the past year or so and they decide to debit my account on 04/12/2015 with R4413.89. My debit order of R565 already went off on 30/11/2015. BEST OF ALL THIS IS DECEMBER!! Now I cannot by Christmas presents for my family as I'm a little sort on funds. I contacted the accounts department and they have no record of such transaction or on my statement. They advised that I get bank statements, go to my nearest 8ta store and open a case, which I did. No reference number was given at the store as the agent advised the system does not represent one. He advised that an Telkom agent will contact me in the next 2 days. After 2 days I called Telkom again and the agent advised that no case was logged on the system. Emailed the bank statements to her and received the reference number ***0.<br> <br> Now my question is how do I get my money back and who do I invoice for the bank statement and time spend resolving this issue? Surely this is also ******* to debit someone's bank account without their consent or knowledge.