Unauthorised debit order

I called the ********** 043 number to try and get assistance to which I was told that there are questions they need to ask in order to be helped & should I fail these questions I will not be assisted. I failed the questions and I was not assisted which is fair. But now I need to understand as to why money was debited by Capitec on the 15th instead of the 25th as I had agreed on their contract? and at what point does Capitec bank have a right to do as they please with my account? Does this mean that the same amount will be debited again on the 25th?

Your prompt response on the matter will be highly appriciated