My mexican uncle insists on calling me Raquel because it either is my name in Spanish or is as close as it gets to my name in Spanish. One or the other, I can never remember.
My mother calls me Rose when she's upset with me, and my friends constantly shorten my name, Rach, Rachie, once it was even Roach. (I'm at a loss with that one).
Other than that, I don't really recall someone mistakenly calling me something else. Quite a bit of people have called, and still call me Julia. They do that on purpose though.