Unsweetened Ice Tea

In the past week, I've been to 4 different restaurants. Not a big deal to some people, but a fair number for me! I ordered unsweetened ice tea at each one (OK, I'm boring, but I don't like lemonade and I'm trying not to drink soda). At 3 of the 4 restaurants, I got diet iced tea aka iced tea sweetened with saccharine. Since when has it become acceptable to give someone diet iced tea rather than tell them that you only have sweetened iced tea? Saccharine, commonly used to sweeten diet soda and iced tea, has never agreed with me. So if they told me that they only have diet, I would have ordered something else. However, I know people that get violently ill from consuming saccharine. What if these restaurants served them diet iced tea instead of unsweetened iced tea without telling them about the substitution?

When will restaurants realize that sometimes you order something a certain way because that is the only way it won't make you sick?