Impossible situation

I called in June to change banking details. Months passed by without any debit order until I wrote an email to Telkom last week. They responded to say that the consultant didn't save my banking details which is why there were no debits. I was asked to pay R600 that they couldn't justify. They said they would lodge a case that would take 72hours. I have asked them to reactivate my line since I have made a payment for June&July since there are still sorting out the billing query but they are refusing while the mistake was on their part. Please help