[m0nty]

Yup, just hang up: it's not as rude as they're being to you. As for the unwanted emails, I set up Gmail filters to forward emails back to the sender (and delete the original) if I don't want to hear from them. Most of the time, I think they assume the message bounced, even though it's not a bounce message. I suppose additional mischief could be made by forwarding the email to everyone at that company, or to a rival recruitment agency, etc.