Go to your local bookstore. Accidently shake out all the subscription litter cards. Drop them in the mail for processing. Send a message.
Go one better, you know how in the corner it is stamped “Postage free if mailed in the US” - just go out to your back yard and find a nice concrete block, wrap it up nice in brown paper, and then glue the card to the top and drop it off. Kind of wakes them up a little when a few cent card comes back at $20.00 postage due.