Withholding tefund

My Insurance Co rented car for me from Avis. I paid deposit of R1500. They acknowledged that I will get full refund. 5 November it was 4 weeks and no refund in my bank account despite phone calls, personal visit to branch and insurance agent getting involved. This to my mind is unacceptable. I am paying interest on my credit card while Avis is using it to plug some financial holes.