Take the pre-paid envelope, cut out your name and address from the cover of the envelope it came in (so they KNOW who it came from), and tape the pre-paid envelope to a brick... The first time they have to pay postage for a brick, they 'should' get the message. MacWorld was one of the worst offenders I had who continued to demand that I pay for a subscription I didn't want or ask for. When one brick didn't work, I mailed them two. When two bricks didn't stop them, I mailed them a 16 pound rock. Of course, I had to put the rock in a box.I also wrote my name and address on the rock with a note that said, "From Montana, with Love". Can you imagine the postage they had to pay for it?

 Don't sweat the petty things, and don't pet the sweaty things!  ; )