Clutch damage after 5000km, race disputes

Hello, my father had to have the clutch replaced after 180000km. Now after 5000km the new clutch has already given up the spirit. The workshop makes a bill. My father is forced to pay under invoice reservation to get the car. Mazda refuses to afford replacement. In my opinion it should still be a guarantee damage. Does anyone have suggestions for the further procedure? Thanks in advance Klaus