Lol, I've been told that too. Sound effects, multiple character voices, accents... yeah. Amused, amazed, dumbfounded and PO'd. Yup, a full range of reactions. Oh, and being told to slow down because they "can't listen that fast". Haha.

I like SmokeyPoole's idea of a set phrase recognizable to both parties. Somehow it seems easier to take in than a whole explanation that they're going to take too long to spit out anyway, further annoying you. Because, I don't know about you, but I probably talk fast more often than I realize, so yeah, someone would have to say something. And it would undoubtedly be easier on them to have only a short phrase to try to squeeze into the barrage.

Learning to slow down? Guess it would be a matter of being aware of it, trying to recognize when you're doing it and then making a conscious effort to slow down. And practicing. Probably lots of! One situation that I've worked with is leaving a phone message. Two plusses. One, they actually stand a chance of understanding the callback number when they listen to it. Two, it's short enough duration to stay focused on staying slowed down.

Ummm, enunciating? Clearly enunciating your words would have a slowing effect. (Just don't do like I do, tending to only use this technique in annoyance...)