Horrible experience with service!

Horrible experience with service!
Made appointment 3 days in advance of the day I was able to come in. I specifically clarified that I only had a 2.5 hour window of time wherein to be there waiting and asked if this was possible. They assured me it was and made appointment for noon.
I took my truck there, asked for the same person I'd talked to on the phone, gave my reservation number and reiterated my need to be able to leave in 2.5 hours.
All I needed done was coolant drained in replaced in my deisel.
They assured me once again this would be NO problem.
Took my truck, came back ten minutes later (I suppose I should give them THAT...at least I didn't wait 2 hours) telling me the "only problen" was that now they were "running into" lunch hour so now my truck would take longer.
I could not wait that long- as explained t9 them 2 times previous- so, I just asked for my truck and left.
Why schedule an appointment for NOON if lunch hour ceases all production and customers have to wait the entire time?
Why couldn't this have been told to me when I made the original appointment for NOON!?