MTN Debit me more that 3 times my monthly amount!!!

I admit I was late with a payment this month but rectified this by the 21st of the month and was assured by the consultant on the other end of the phone that all was in order. Now, 9 days later MTN debited my account for more then three times my normal debit order? When I phoned the call center the consultant she could not explain why so much had been taken off only that I had been double debited and that I should go to the bank... Super helpful?!? So what is the other amount that was charged, and how can I get it back?? PLEASE CAN SOMEONE SORT THIS OUT?