Get a lot of junk mail? I use to. Credit card offers, things with postage paid envelopes have stopped comming to my house!
Simply take the return envelope and fill, no STUFF it full of everything they send you and more and mail it back to them!
You may have to do this a few times. And for the more persistant senders, simply paste their envelope to a box and fill it with "goodies" and ship it back to them!
Word will get around not to send such mailings to your house, and you will be taken off mailing lists.