AFRICAN bank, i dont owe you

according to them I owe them a freaken R6.45 on my account that I do not know where it comes from because I have NEVER missed an instalment , I have spoken to their consultants which have proven useless to me as no one has attended to my complain. I want to know where that amount comes from and how it came about. This is how you earn your BAD REPUTATION and mess up customer's credit scores. I want answers