I hear the phrase "Not Interested" many times every day. More often than not it's before I even get into what we do here and how it's going to benefit their business. I think people believe that by telling me this that I will stop calling them.
Wanna know a secret? I don't. The only way I'll know you are truly not interested is if you give me a logical reason that you are not interested (after I've talked to you about our product), and/or you explain to me why. Otherwise I know you just don't wanna talk ... for now. Thus, you'll keep getting called. Same thing goes for folks that just slam the phone down on me before I get into my schpiel.
On a philosophical note, this job has taught me something: Be Nice. If you're not nice then bad things will keep happening to you. You wouldn't believe the data trafficking that goes on in the world today. People can know a lot about you very easily. Thus, be nice and you'll likely be treated the way you would want to be treated.