Fuck 'em! I've got loads of different tactics depending on my mood and whether I can be bothered.
1. "Have you had a car accident that wasn't your fault?"
Me - "yes I did!"
They get so shocked they put you through to someone higher up! They ask me the same and tell me I can claim blah,blah.
Me - "it's ok, I've decided I don't want to claim because my injury was only a lacerated penis and I don't use it much anyway!"
2. "Do you want to save money on your Electric?"
Me- no thank you.
"You don't want to save money?"
Me - no, I like paying more!
3. "We've noticed serious viruses on your computer"
Me - I don't have a computer! In fact I don't have electricity or gas! (I also use this for no.2.)
4. "Are you interested in Double Glazing?"
Me - sorry, I don't have any Windows.
"Are you sure you don't have any Windows?"
Me - are you calling me a liar?
Finally, if I can't be fucked to do that ,
5. "Are you interested in double Glazing?"
Me - Yes I am actually.
"They start their spiel, and I say "oh yes" like I'm interested! They then start talking, and I leave the phone on the Side and carry on doing what I was doing. 15 minutes later I go back and put the phone back on the hook.
I got caught out once as the guy was still on the phone when I went back, he gave me a shitload of abuse and I pissed myself.