That's hilarious... I've definitely mistaken phone solicitors for friends before too. Here's a call I still remember:
TS: Hey-
Me: Yo, what's up Josh? Tryin to hit a blunt? I got some maui waui (sp?).
TS: ...
Me: You there?
TS: We're calling on behalf of the Lutheran Church, Missouri Synod to thank you for your generous donation. *Click*
One of my finer moments to be sure.