Mtn taking money.

I paid my mtn bill via the mtn app then they still debited my account and after it was reversed automatically 3 times, each time there was a R120 taken from my account due to an item being unpaid plus 2 times an extra R100. That comes to a total of R560 extra cost to me and still mtn just send me a msg that my account is unpaid and my outgoing calls will be stopped, I think this is unacceptable.