Don't sign up with Avo Marketing. Its hard to get rid of them ... even when you unsubscribe!

I have been trying to unsubscribe from Avo marketing for months now. They have emailed me and stated that my email address has been removed from their database and that I should not receive any more emails from them. I have since received 8 more. Each time I tell them to stop sending me emails I don't get any response. Please help.