I have a Nedbank home loan, and they did not deduct the payment this month

I have a Nedbank home loan, and they did not deduct the payment this month. When I called them, they told me the deduction was made from the wrong account. I really don’t understand how that happened, because they’ve always deducted from my account. I’ve phoned several times, but no one can explain how the deduction came from a different account, whether I will be in arrears, or what the way forward is.