Penalty fee for funds paid on time.

I received my April statement only to find out that I was charged R70 for failed debit order (penalty fee). The thing is I made an EFT payment first before cell c tried to debit my account because as always, they never debit my account. I have always made EFT payment and was never charged a penalty fee. How can I be charged a penalty fee when I paid my contract on the same day that I was debited? This is unaccepted, and calling cell c is also a nightmare. (2018-04-11 around 10:30) I called and spoke to a consultant by the name of Emmanuel Moloi, he could not give me a direct answer why I was charged the amount. Then I also made thing worse by asking to change my method of payment to EFT- I was informed to get a letter of retrenchment from my employer or go to the police station to say why I need to change my method of payment to EFT. I MEAN REALLY, IS THIS SOME SILLY JOKE! Why a letter of retrenchment when am still employed and not being retrenched, and why involve my employer and the police in my personal matter? When I took this contract I didn't go to the police or my employer for approval, but to cell c. I need the R70 removed from my statement and my method of payment to be changed to EFT because I can't be paying penalties for funds that were paid on time. As for your ****** consultant am still waiting for his supervisor to call me after being on hold for almost 10 minutes. Apparently all the supervisors were busy "assisting other clients".