Unauthorized Debit Order

I noticed an unauthorized Debit order that went through my cheque account and immediately called the Nedbank Contact Centre. When querying the transaction I was then told to call Nedbank Retail Recoveries who then referred me to Nedbank Legal. The numbers provided were both incorrect and could not get hold of anyone. I have now spent two days trying to get hold of them in order to understand what the transaction is all about. I am told the transaction cannot be reversed internally but still failing to make contact with whoever is supposed to provide more information. I feel I have to change my Bank as Nedbank can just decide to debit my account without my authorization then put me from pillar to post. I will also be logging a query with the Ombudsman to get this resolved. I even went on to send an email to my Branch and there has been no response. I called my Branch and they told me to call the Contact Centre and nothing really help.