Refund payment not forthcoming.

Waiting for a refund of my installment that went of after I settled the vehicle. Numerous phone calls since the 1st of March and still they have not paid my money back. Promises every time but nothing happens. Always some issue or excuse from the call center agents. I require my installment to be paid back plus 18 days interest. I currently view this as theft and will make a case with the SAPS if payment is not forthcoming immediately.