Debit order refund

Settlement amount on my car was received last week, and was valid until 2 November. Full settlement amount was paid by 21 October. Normal debit order of R3500 odd went off on 30 October. When enquiring about having the debit order refunded, seeing as full settlement as received from ABSA, was paid before 2 Nov, I was informed that the full debit order will not be refunded and that only an amount of R2800 odd, will be refunded. Although the consultant was very friendly, I struggle to understand why my full debit order is not being refunded (consultant could not explain), and why I essentially have to write off almost R700 on a car that was settled in full before validity of settlement amount expired.