@Yusuf Smith The Direct Marketing Association has a mechanism to opt out of getting mail.
"The Mail Preference Service (MPS) is designed to assist those consumers in decreasing the amount of national non-profit or commercial mail they receive at home. This section will tell you how to use MPS. The Mail Preference Service (MPS) is a consumer service sponsored by The Direct Marketing Association (The DMA)."
Here's a link to their information page:
http://www.dmaconsumers.org/offmailinglist.html - Or you can suggest that they google "DMA mail preference"
Reputable list compilers run their databases against the suppression list with every update. Ask your provider if the list you are getting has had this done.
If someone complains it's usually because they have received too many solicitations. Time to think about marketing to a different segment. At the very least, keep track of the complaints and scan all future lists for those names and take them off.