Nedbank and MFC Poor Service

This guy's charged my account twice. I called them the whole day on Wednesday to request my refund. Their staff took me frok corner to post without any help. I even send them my bank statement which proofs that they have debited me twice. To this date they failed to assist me. They send me an email saying i owe them.

But what if it was me failing to pay them? Why are they not helping me? This is bad