Thrifty Tries to Stiff Customer for Excess Miles

These people had me sign off on two separate documents stating two separate figures for mileage on the vehicle that I rented. I didn't notice the discrepancy and neither did the guy who prepared both documents -- unless he was purposely trying to stiff me. I watch for gas level, I wasn't accustomed to worrying about mileage bcs in the past they never charged for mileage. Anyway, my plans for why I rented the car didn't even come through and I got caught up working, had the car parked for most of the time I had it. But then when I returned the car, Thrifty is trying to hold me responsible for putting 3000+ miles on the car. They're saying that the lower mileage out figure is the accurate figure even though the 3000 mile higher figure is the accurate one. They're totally trying to stiff me; because I was too trusting and not paying attention. PLUS they didn't verbally tell me (it was in the fine print) that they were going to start charging for mileage because I would have known to make sure that they had that mileage figure correct on both documents. They're shady, folks.