ABSA bond account closure non response

I had discovered that ABSA had charged a deposit fee of 4.9% on a deposit that I had made. I requested substantiation for the charge and was sent a statement from 2013, where on a footnote on the statement it was mentioned that a fee would be charged if payments were made over and above the actual monthly instalment. I sent a request for the legality of such a fee and where my informed consent had been given accepting such a charge but have not yet received a response. From internet research I discovered that normal cash deposit fees at ABSA are between 1 and 2.5%???. They have also subsiquently charged me interest on the "outstanding" balance that remained because tgey had deducted the exhorbatant fee from my oayment