debiting my account without permission

It's now the 3rd month in a row and I have come to a point where it's no longer a game! After all the phone calls, staff putting me on hold for no reason for over 30 minutes and after making a fair arrangement to debit a limited amount for my c/c every month, you feel the need debit thousands of rands off my account? Even after i have CANCELLED my debit order, you once AGAIN do as pleased on my account this month without my permission. I have been with std bank for over 15 years & the service just seems to be worse by the years! Please advise what needs to be done here because I'm finding it very difficult to keep this account with you?