Contract question

I took my car in for tire pressure sensor. Dealer sent the request to approve the repair. They say I’m 500 miles over on my expiration mileage. I said no I’m not and I looked at my contract that’s states I still have 10,000 approximately left and 2 years left. The dealer calls the warranty place and they say nope OP is over 500 miles.
Come to find out when the dealership wrote up the contract they put the wrong starting contract sale mileage at 56,000 when it was actually 45,000 miles. The contract that’s was signed by the dealer says I still have about 10,000 miles left under this warranty but at this time they are actively trying to say they won’t honor it. What do I do?
This is in central Wisconsin