I've run into sales clerks like this before, or a service person over the phone. I usually say something like, "Now hold on there honey, I'm Southern and so I promise to speak faster if you'll promise to speak slower, k?" They usually laugh and DO slow down. If they don't, I just sit quitely until they say, "are you still there?" at which point I say, "Un huh, I'm just waiting on my brain to catch up to warp speed."

Again...laughter follows, and we usually meet in the middle.
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Queen JJ
www.queenjawjaw.com
All Things Royal - 2010 and Beyond
Humorist for the NABBW