I once wanted a McChicken, and they gave me a BigMac. Then I asked for the right thing and they AGAIN, sent me a BigMac. I asked (getting pissed of now) for the correct order, and they started getting angry with me. They then sent me Chicken Nuggets, and I asked for my order, FOR A FINAL TIME, calmly, and then they started swearing at me. After a 3 minute swearing match between me the cashiers and the manager, I finnaly got my sandwich, but now I'm not allowed in that McDonalds again.
(It's been 1 year now, and they still have that ban.)