The only thing that comes to my mind is this: If you want him to stop contacting you but don't tell him you no longer want contact, you can't really blame the guy for continuing to try since I don't think we should expect people to read our minds...
I know all too well the nonsense that arises when you try to talk to an A so I like Mike's idea of an email. That way you say it but don't have to deal with a response.
But we are each individuals with our own comfort levels and whatever YOU feel most comfortable with is what is best for you.