Our 2017 Forester's AC stopped working after drivi...

Our 2017 Forester's AC stopped working after driving it for only 20000km, and we came to the one in Mississauga to get it looked at. Our warranty still last for a while at this point in time but when we got it looked at, they said that a part is damaged due to an external objecting hitting it from under the car. The part will need $800 to replace and taking a look at the car itself took $200. This is crazy, what is the warranty even for then?