Useless bank

I am struggling with an unauthorised debit order ..of s ound R3.500 Absa is of no help.ibhave explained countless time that I have no idea about the creditors who's trying to debit my account and I did not approve any Debi check .but I'm getting no assistance in regards with that.being rols countless stories and that I should contact the 3rd party company that is trying to debit my account. How do I contact a company I dnt even have any dealings with them ..all I ask is for them to investigate who approved the Debi check on my behalf.tgey cnt do that as well.