Why is Plain Different Out Here (or I don't want mayonaise with that!)

So one of things I have noticed in the past little while is how something like ordering food has become a little more confusing and problematic.

Case in point #1: A few months ago, I ordered a burger at a joint and asked for it plain. The girl behind the counter looked at me like I'd ask her to give me all the money in the till, went to I assume a supervisor, who came over to help her with the order. "He wants nothing on it but ketchup and musturd," she said. "No," I explained, "I ordered it plain, that means I want nothing on it." She looked at me, looked at her employee, then told me I was mistaken, it means what she said and punched it in that way. After a two discussion, in which she kept telling me I was wrong, I finally got in her head, I wanted nothing on the burger "the meat and the bun" we say. I received it, after dirty looks by the staff and by the people who were behind me. I now know, don't say plain, say nothing on it.

Case in Point #2: I went into subway a few weeks ago, and order a chicken parm sub. After ordering my bread and asking for it to be toasted, I went to further down the line. It came time for my sandwich to be given its coverings, I stated, "nothing on it please." "Mayonaise only? Ok" was the response. I don't know where you get mayonaise from nothing, but it happened (2nd time in my life, but that's a Florida story). When I explained I didn't want anything on it, instead of just going along with it (and making her job easier because she doesn't have to put anything on the sandwich), she told me that nothing on it would include the mayonaise. Again, regardless of that, it is not what I asked for. It took another two minutes to get my sandwich. She gave me that look (one I gave many times while working in the service industry) of me being the biggest pain-the-butt customer she had all day. I learned another lesson, tell them exactly what you mean.

Case in point #3: Last week, I order a chicken sandwich, and I stated, just the chicken and the bun- plain - nothing on it. The young man behind the counter nodded his head and stated "only mayonaise and lettuce." This time my voice was a little higher - "where did you get from what I said only mayonaise and lettuce?" He told me I ordered basic, and that's basic. I didn't order basic I told him - i ordered nothing, explained exactly what I should be looking at when I receive the sandwich. He nodded, "I get it, you don't want mayonaise, you want something else on it." I lowered my head, caught my breath, and explained one more time what I wanted. "I've never heard of that," said the young man behind the counter. "I'm sure you haven't when you don't listen to the customer," I thought. This time, five minutes later, and I checked the sandwich in front of him, I was able to get my food.

So, among the many differences out here, this is something I never would have thought would cause me this many problems (this is only three examples). So short of me walking behind the counter and making the sandwich myself, I have to keep just explaing, with hand gestures to help. Or maybe look up a new word for plain, nothing, basic meaning meat and bun!