Debiting my account before pay date.

I am so unhappy since December 2021 Nedbank have been deducting on date we did not agree on. In December 2021 they deducted on 15th and I did not have sufficient funds as I get paid on the 20th as per my agreement with them. My credit bureau was impacted and I had to pay R300 unpaid fee. Again now in February 2022 they doing the same thing. They deducted the money on 18/02/2022 and now I have to pay again R300 of unpaid fees with my bank because of them and also my credit score will be impacted. My agreement with Nedbank is 20th of every month and I only get paid on 20th not before. I need my money for the unpaid debts and also they impacting my credit score. I complained last month and it seems it fell on deaf ears. This not fair.