While not exactly a service incident, I had a similar experience recently  
when I bought a new truck.

I had picked out the vehicle I wanted and after a little haggling we  
agreed on a price. I wrote them a check for the down payment plus tax
and license and told them I'd be back that evening to pick up the truck.  
When I returned, I had to wait about an hour before the finance guy could  
get to me. When I finally got in there, everything went smoothly until he  
started adding up the numbers. He then discovered that they had  
miscalculated the tax & license by about $150. He then said he needed  
another $150 from me. I said we had already agreed on a price and it was  
their problem, I wasn't giving them any more money. The finance guy then  
brought in the manager on duty who proceeded to give me a hard time. I  
reminded him that I was the customer and I didn't think I should be  
treated like that and that if he didn't back off he could forget the whole  
deal. He made some smart remark so I told him where he could stick it,  
snatched back my check and left. Needless to say, they were not pleased by  
the turn of events.

Early the next morning I got a call from the general sales manager wanting  
to know what happened. I related the story and he apologised profusely and  
asked if there was anything they could do to change my mind. I told him  
that if they gave me the truck for free I probably still wouldn't take it,  
that there were other dealers in town, I was a repeat customer of theirs  
and that they should learn how to treat customers,etc,etc...I was still  
pretty steamed about the whole affair. He gave me the line about hating to  
lose a customer and they would try to find a solution, etc, etc. I told  
him not to bother, thanks, I'd go somewhere else.

A couple hours later, the owner of the dealership called me, all  
apologetic, etc, etc, etc, and said that they would cover the $150 plus  
knock another $400 off the price of the truck. I told him I'd think about  
it and he gave me his private, direct phone number, his secretary's name,  
and assured me that they valued me as a customer, etc etc etc....

I thought about it for a few hours and discussed it with my wife and we  
decided, what the hell...that was a pretty decent deal, so I called him  
back and accepted his offer. When I went back the next day to pick up the  
truck, I received the royal treatment. Everyone seemed to know about the  
incident, even the lot boy. Everything went smoothly and I was out of  
there in my new truck in about 30 mins.

So, I guess I'm a reasonably satisfied customer. However, it should not  
have happened in the first place. I was a bit shocked to have a sales  
person talk to me like that. I don't expect them to bow and grovel, but I  
sure don't expect to be given a hard time either, esp. when it's their  
mistake.

Anyway, I'm happy with the truck and it turned out to be a couple hundred  
dollars under invoice and they paid most of the first year's license fee.  
I'm not sure whether I'll go back to that dealer, tho.