Unauthorized Debit Order

On the 01 April, I paid my instalment for April and on the 15 April, I made a substantial payment—15 times more than the expected amount—into my Absa credit card, which I obtained via Woolworths. This payment was intended to cover my May instalment, as I had already settled the March instalment. However, to my surprise, Absa Bank debited R1,821.00 from my Nedbank cheque account without my authorization, despite my prior payment. As a result, my cheque account was overdrawn due to this unplanned debit order. I would like to understand who authorized this debit, as my agreement with Woolworths stipulates that I make direct payments to them, which I have consistently done each month without fail. I would have understood if the account was in arrears and the bank needed to recover their monies. In this instance the account is in good standing. What gives Absa the right to debit my account without my consent

I will also raise the unauthorized debit order matter with my bank, Nedbank to understand how my account was debited without my concern.