I have found that saying the magic words,

"I'm sorry, but my parents aren't here"

... will make a telemarketer ... go away ... fast!

Another effective way to meddle with a telemarketer would be to
sound like a slow 5 year old and say,

"You should talk to my parents
... but I don't know where they are
... I haven't seen them since they left the house 3 days ago"

--
Martin

p.s. After using method #2, don't be surprised if you get a visit from
Child Protective Services.  Too bad they won't be as easy to get quit of.