Telkom bad billing system

I have a WiFi with telkom and they billing save sucks big time. They debit me as they please and not as per our agreement. Debit amount is supposed to be R303 but they just debited R2481. On top of that my debit order date is the last day of the month but they debit me on the 26th the moment there are funds in my account and they don't debit the agreed amount. I have complained about this a number of times and nothing changes. Telkom your billing system is bad very bad I can't wait to close my account with you, I will not do business with such a company who do not even know how to communicate with clients.