What about telemarketers? I've never invited them in, and still they call. How am I supposed to “revoke” an invitation that I’ve never even “extended”?
The invitation rule is hard and fast, I’m afraid: when our vampires get in, they do so by invitation only. So you did invite them in, only the trouble was you didn't know about it.
Vampires are experts at diversion, deception, and shape-shifting, and we often don’t realize we’ve extended an invitation until we're down a few pints. Telemarketers, I think, are especially endearing in their tactics -- often requesting "just a moment of our time," or sometimes offering us "valuable savings" and even "prizes" to try and get us to open up. What many of us fail to understand, however, is that by simply responding to their questions and offers, we extend our invitations.
As to the solution, getting on "no call lists" is okay, I guess (I'm not so sure I want to be on anyone's list, however!) but not in the least bit necessary. When a vampire calls and says to me,
"Hi Claudia! This is Paula, calling from Blopiddy-blah..." I always interrupt (politely!) and take control of the threshold, the invitation, and the vampire by saying:
"Hi Paula! Would you please take my name off your list?"
There really isn't too much a vampire can say to that besides, "Yes I will," or "thank you, Claudia." Since it's a bad idea to lose my manners around vampires or anyone else, I usually end our (always brief) conversations by saying something like, "And thank you, Paula!"
This is what my friend Cindy calls "bagging a vampire," and I've got to tell you -- once you've tried it and found out how good it feels, you'll never want to stop.