The Ban Telemarketing Petition
They call you because you have made your details known 'somehow' to a company - just like email SPAM, you have to be careful who you give yr personal details to. Fill out a competition form = permission. You don't HAVE TO talk to them, so just say "no thank you". DO you get this cranky when people call your phone number by accident? No, I dont think so.
Two more points: telemarketers get paid VERY VERY well (after all, they're just normal people doing a job), and they are researching things and opinions that will effect and change companies and services in the future. Believe it or not, they actually DO listen to what you have to say about things.