FNB - credit card unauthorized debit order

Turning to this forum after a very disinterested, rude and unhelpful service consultant "assisted" me with my query on a Debi check mandate from my credit card, which I declined on my FNB app.

My credit card is always paid in full plus extra on the 25th of each month, if I used it during the month.

The SC told me they will debit my cheque account on the first of the month regardless of my accepting or rejecting the Debi check. What's the purpose of giving me an option? The answer was if I use a credit card I owe them money. Very professional and enlightening!! My reply was then Id rather close my credit card. Her "friendly" response was in the lines of, can I request it to be closed?

Then I saw the email sent by FNB on 25th of October to notify me that a debit order for the amount of R9482.75 (based on usage - you got from where??? ) will be deducted 1st of November 2021. I transfered R3000.00 to my credit card on 25th October 2021 to cover my expenses of R2875.24 for the month. Credit card now showing positive amount.

How can a bank take money you don't owe out of your account without your consent?? Do I need legal assistance here?