In my experience most won't hold for that long.
What's fun is to play along. Act interested. Give 'em buying signals. Keep at it. Let 'em close the deal and then when all is said and done and they ask for your credit card number pretend the guys in white coats at the loonie bin have caught you out of your room again. Scream and shout. Always good for a laugh.
Another good one is after they've started in on you with their sales pitch slowly begin acting like your better half has walked in and is doing their best to seduce you. Use your imagination.
Keep in mind that to the phone folks time is money. the more of their time you take the less money they make.
I like to speak jibberish when they call.