Instalment not paid error. Getting spammed the following days. Wants me to pay a penalty fee for the remainder of the period

My debit order for my VAF goes of successfully on the 25h of each month in the evening. What follows the next two days are calls, WhatsApp messages and SMSs stating that my instalment was not paid. On my detailed statement it shows that my payment was rejected. I tried contacting the VAF department, and they are unable to help, and want me to pay a penalty fee for each installment for the rest of my contract period, since I'm looking into changing the date, to reduce the spam coming through. This is clearly a system issue on their side.

I requested an initial callback, and I'm waiting almost 2 weeks for them to get back to me. When I phoned today, I keep getting transferred from department to department trying to get someone senior and with authority to call me back or to even escalate this matter