How do you stop telemarketers from calling. I tell them to take our number off their list, but they don't.?

I tried that thing they came up with on line in Canada where you give the gov. your phone number and they will put you on a list for no telemarketing calls. Then had to remove my number from that list when they list got stolen on line or something and sold to telemarketers and I got even more calls. My best defence is call display and a three ring for long distance calls. As there are few friends or family out of Canada I know the long distance ring tone is a telemarketer. The call display tells me if it someone I know too... :-)