[Bushleague]

I've always found that removing your car from the auto shop's parking lot before you haggle over the bill tends to help. Theres been a few times that a disagreement over billing appears to be going nowhere until I mention... "Just so you know, all we're arguing over is the spare keys"... usually followed by a complete change of attitude.

Sure, if they really wanted to get a collections agency after me I'd have to pay what they want, but I think trying to collect on unpaid bills is more of a widespread problem with automotive shops than most people would think. If the conversation looks like its headed in that direction and the shop realizes they dont hold any collateral, they would generally rather trim the bill than get caught up in another unprofitable dispute.

I'm not saying that this is how business should be done in general, but in blatant examples like where the shop is billing for more hours than the vehicle was actually on the premises, or trying to bill for fixing damage that they caused... bring the spare keys and a buddy, play nice until the vehicle is gone, then start the negotiations.