Geoff B., I had a similar bad experience.
I ordered a chicken sandwich at this restaurant without mayo -- after waiting quite a while (I was one of two people in line), I finally received my sandwich. I checked the sandwich outside, just to be sure it had no mayo...it did. I returned, told the man who took my order (perhaps the owner?) that the sandwich had mayo -- he grabbed it from my hands, and gave it to one of his workers, who then came back with it about two minutes later. I thanked him and left. I again checked the sandwich when I got outside, and saw that the bread had been replaced, but mayo was still all over the chicken. I returned to the restaurant and told the man that it still had mayo, the man yelled at me and slammed the sandwich on the counter, insisting the sandwich did not have mayo. I showed him that mayo was still all over the chicken and asked for my money back -- a nicer man from the back of the restaurant thankfully came out and apologized and returned my money.
Perhaps it's time for the younger gentleman to take over management of this restaurant.