Champion Hyundai Houston Complaint

I took my car to Champion Hyundai of Houston. I needed some warranty work done. I told them a belt was squeaking. They recommended changing the timing belt for $500. I didn't realize the timing belt was changed a year earlier. I knew the crankshaft position sensor was changed a year ago, but I didn't know they had to change the timing belt to get to the sensor. A timing belt may need to be replaced just once in a car's life. This information was in their computer system. They could have easily looked it up before doing the work. I trusted them to do this. I made this discovery when I was looking at the invoice from the ealier service from another Hyundai dealer. Even though it was from another Hyundai dealer, it is still in the Hyundai computer system. Champion Hyundai should have looked up the history before recommending service. They should refund my $500. They refuse to.