Capitec un authorized deduction the norm?

Capitec have send me an email saying I may, if need be, pay my monthly payment on my loan earlier in December 2023, I just have to confirm. BUT, as I only get paid on the last day of the month I haven't rep****. On the 20th of December 2023 Capitec deducted money from my other account without authorization, when I called in to customer care my calls went unanswered. When I called on the 28th December the customer service representative could not help me and put me through to the collecting department and the phone died in my ears. This was the second year in a row. What about the interest as the moneys get deducted earlier?