Filled diesel vehicle with petrol

on 29th Feb petrol attendant at Shell in Sundowner accidentally filled my diesel vehicle with petrol in stead of diesel. they vowed to pay for the drainage and repairs. After settling the R4985.16 bill with Audi in Fourways on my credit card, they now ignore all my requests to refund me. Have phoned their area manager 3 times- also ignores my calls.