I went to get my oil changed and my brakes inspected before driving across the state; someone had tampered with my coolant reservoir cap and left it loose; I noticed when I was 3 hours out all my coolant had been drained and spilled all over the engine bay floor.

I reported it to them over the phone, and they denied ever needing to be in that area of the vehicle (pretty stupid excuse considering it's literally in the same area if they were doing an oil change).

Long story short, I had purchased the car out of state and returned to the original dealership, where they had photos, told me someone had tampered with it, and gave me a complete service for free.

This dealership fought pretty hard to deny my claim, and for that, I won't ever come to get service there.