unauthorised billings

My debit order for June bounced and in July R499 was debited and I was then advised of the month outstanding, I requested they double debit end of August R1009 which they did but 2days later my account was debited again of R149 I called MTN and no one could advise what the amount was for and they said cause my payment was successful and account up to date I need to reverse the money with the bank and they will log a query and only advise after 5-7 working days. I reserve the money with the bank and was charged the reverse fee but no one from MTN ever called me back. this month my account was debited of R848 and upon calling mtn this morning Noluvuyo could not advise what the amount was for and said she will have to log a query which may take 3-7days to resolve (***). I advised that was unacceptable and that I need to speak to a manager she told me that her manager Elton Ellias will call me within 2hours. I called back and spoke to Chad and Justine who both kept telling me about procedure of logging call as they did not know why I was double debited. is MTN ******** me? Why is procedure followed when I want my money but not when the debit my account without my consent