When a collector calls your house asking for someone who doesn't live there and never has don't say "No they aren't here" and hang up. That gives the impression that this is a correct# and gives a collection agency grounds for believing this number belongs to the debtor and that you are a liar when they call next and you say it is a wrong#.
Also, never take a message for someone you don't know because you think it's going to get the calls to stop. It isn't.