Payment not allocated

I paid an instalment of R 540.68 on the 15/10/2025 at their official website in my profile. The issue is that the payment was not allocated, and it still says I owe the instalment. I reported the issue immediately at their customer support portal and explained what happened. Since then no help, and they are still trying to withdraw the amount from my account again and added a cost for being in arrears for that instalment. The statement number is ***.