If you get repeat calls from the same
telemarketer (and don't assume that because it's from a
different company that it's a different telemarketer), merely explain that the
FCC promulgates
regulations that require that a company
cease and desist from calling
consumers who request that they no longer receive calls. Tell the telemarketer to put you on its "do not
call" list.
If the telemarketer says that they do not have such a list, reply that they do in fact have such a list (many companies will lie about this, but they are required to keep this list), and that if they do not comply with your request, that you will inform the FCC of their violation.
Stupot says the UK version of the FCC regulation is the "Telephone Preference Service" which is run by the Direct Marketing Association.
There are rules for this sort of thing. Unfortunately, most people don't know their rights.
That said, when they call my parents' house for my dad and my little sister answers the phone, she replies in a sad voice, "Daddy doesn't live here any more. Mommy says he drinks too much." That seems to work too.