Presumptious Debit-Order date change.

I've had a home loan account with Nedbank since 2019 and have been servicing the account regularly since inception of the agreement. The agreed upon debit date was the end of each calendar month. Which they always debited on my salary date(25th).

This morning(23 April 2024) upon reviewing my current account, I noticed an attempted debit which will bounce as I hadn't sufficient funds to service the request.

Attempted to call them and was sent from pillar to post. My frustration is that the funds they depleted had immediate plans and I'll incur bank charges over and above this mishap which I didn't opt in for.

What's even more puzzling is that there is no public holiday around my upcoming salary date, or the end of the calendar month for that matter.