Car badly damaged in Kairos's care

My car was badly damaged while in Kairos's care - the bumper had puncture marks which went through to the metal, as well as scratch marks on the bonnet and around the car, which had been inflicted by a dog. The owner didn't deny anything when we confronted him, but has declined to re-imburse the excess we had to pay the insurance. He has lacked the common decency of doing the right thing. It has cost us so much extra in the end, on top of the inconvenience of being without a car while it was at the panel beaters.