I've only complained about poor service in a restaurant once.... and it was a Subway. I had been to that store and had excellent service every time except that one, and I made sure I told the manager that, too. I ordered a Subway club. Made my selections for bread, cheese amd then, when asked, I replied, "No peppers of any kind, I am allergic" He FILLED my sandwich with green bell peppers, which happens to be the one thing I am highly allergic to. I cannot even eat a tomato or anything which has touched a green bell pepper. My husband made him throw out the sandwhich, change gloves and make me a new one. Jerk-boy attempted to put green bell peppers on the new sandwhich, saying "She can't REALLY be allergic to these."
Well, THAT was what did it. The first time could have been a honest mistake, the second time was deliberate. The restaurant was full, and people were getting impatient, but Hubby called over another employee, explained what happened and asked HER to make me a new sandwich, which she very cheerfully did, and did it exactly how I had ordered it in the first place.
The next morning, I called the manager, explained the situation, and Jerk-boy was fired. Apparently this was not the first or last time he had been rude, disrespectful, and downright hostile to customers who dared to want a sandwich when he was unhappy about having to work that day. Yes, I continued to go to that restaurant, and I never had another problem.... and I made sure the manager knew how wonderful the REST of her employees were.