An old science-fiction-y story, at least 1970s, probably earlier. Silly, short, kind of like one of Ray Bradbury's throwaways or one of Phil Dick's goofier renditions.
I think but am not sure that the name of the story was something like EXchange-2-3566, where exchange is of course the old-style word/location telephone exchange. The exchange, I keep thinking, was 'boojum', 'snark', or 'jabberwock', or at any rate some other Lewis-Carroll-associated beastie, but I am not sure because if that were the case it seems like google should be able to tell me and it doesn't seem to know.
The story was about someone trying to contact a particular exchange with the same first two letters as the one in the title, getting the wrong one (presumably due to 'operator' — in this case literal operator! — error), and being misidentified as part of a secret group. And by the time that they catch on that the bewildered person isn't part of the group, it's too late, and they have to make him disappear. Possibly 'softly and silently', as in Boojum, and we have come full circle.