African bank interest

Please advise why I am being charged between R500 and R900 interest a month when my account is not in arrears?? This is unacceptable as it's almost the same as my installments and the acc is not going anywhere. Please refund the interest of both accounts back to me because my accounts are not in arrears and don't see why I am being charged. I have also emailed CExperience@africanbank and all they do is let the phone ring twice then they put down.. What service is this???