So I'm not mistaken on this point: Do NOT be rude to the person (or machine) calling. These are low-paid workers who do not deserve your abuse. They aren't in telemarketing because they love the job (well, most aren't); they're there because it is a job and they and their families need to eat. Be polite, but be firm. Do NOT support this business model and they will stop doing business this way.
This phenomenon has only gotten worse as companies have been working to unlock our cell phone numbers too. Big business legislation is behind your dinner-time annoyances. We need to hold together or else expect this kind of assault to continue.