I'm standing in line in a strange town, waiting to buy a cup of redbush/honeybush/rooibos tea, the tea so good it needs three names.
There's an angry woman at the front of the line. "Double, double," she says.
The barrista stares blankly. "How can I help you?"
"I'm sorry, do you want a coffee?"
"DOUBLE, DOUBLE!" (At this point, it occurs to me that this might be local jargon for 'double cream, double sugar in a standard coffee').
Sometimes, we get hung up on catch phrases and jargon that work great when everyone understands what we mean, but fail to bring understanding to outsiders. Yelling louder isn't always the answer. Changing your words might work better.
[Graham and others have pointed out that every self-respecting Canadian knows that Tim Horton's coffee chain not only sells the double double but promotes it heavily. So the clueless server was truly clueless. My point stands... when someone doesn't understand what you're saying, saying it LOUDER doesn't usually work.]