De*****ed and Poor service from Bank

A Cheque of R55,000 was deposited and it cleared immediately on a Saturday of 31 October, This cheque was a business cheque from Standard bank and the depositor informed me that it will clear immediately (how did he know that a Std bank cheque deposited into an Absa account will clear immediately on a Saturday ?), within an hour of being deposited it cleared and I released a motor car (was selling my vehicle), I immediately transferred all amounts into my credit card (just to be safe) and 3 days later the cheque bounced. Since then I have been trying to get the Bank to resolve and refund me as clearly the depositor colluded with someone in the bank and I have been unsuccessful, been told ***** dept dealing with it and its now legal and to date no response at all. All cheques were taking 7 to 10 days and no cheque ever cleared immediately before, but I am being sent from pillar to post, being a private bank client has also not helped at all as the service and response to my complain is not receiving any attention. I need my refund urgently.