The passanger didn't put the seat belts and my contribution increased

Hi, maybe my matter is silly but I am very confused. The insurance agency assessed my contribution in the accident on 10% as I had no seat belts. Then they asked if my wife put her (she was a passanger) and when they realised that she didn't, they increased my contribution to 15%! To my mind they try to make fool of me. What should I do?