MTN TAKING UNAUTHORISED DEBIT ORDERS

I changed the date of my debit order from the 1st to the 5th for the reason being that I started a new job and my salary date changed, this is to ensure that my money is in the account in time for them to debit. Debit order went off on the 1st of June, and then conveniently another debit order of DOUBLE my monthly payment goes off. After speaking to a lady in the customer service department demanding to eventually speak to a manager she advised me that she will send a request to the collections department BUT she cannot guarantee that they will phone me back because they don't really make or take calls?! *** how does this work?!? I sent a message on the Facebook page and ended up speaking to a lady there where she advised that I did not pay for this month but next month's debit order will go off, if you use your knowledge, 1st June - payment done, July-payment sorted (as I am in credit) August - payment will be taken off my account,... LIKE WHAT THE F**** how on earth does this work? Now she wants to tell me: "Please be advised because you changed your debit order date you are not debited one month in arrears anymore. When your invoice closes on the 20th you will be debited on the 5th of the following month. Prior to changing your payment date when your invoice closes on the 20th, you were debited on the 1st of the following month" THIS IS EXACTLY THE SAME JUST A DIFFERENT DEBIT DATE! I did NOT give them authorisation to take any additional amount from my account NOT EVEN TALKING ABOUT THE ADDITIONAL AMOUNT BEING A DOUBLE MONTHLY INSTALLMENT.... I am disgusted! I will most certainly make sure that everyone knows that MTN wants to let their customers bite the short end! TAKING UNAUTHORISED DEBIT ORDERS!