There's a magic phrase that makes telemarketers stop telemarketing and politely say goodbye.
The magic phrase is "Put me on your do-not-call list." When you say this, almost every telemarketer will say something polite, like, "Thank you, sir," or "We're sorry for the inconvenience."
Saying the magic phrase is better than simply hanging up. If you just hang up, they call again another day. If you tell them to put you on the do-not-call list, they put you on the do-not-call list. Then they do not call. Magic!