Many people hang up on telemarketers, but others will listen politely to their pitches even if they are not interested in the product. Telemarketers know that anyone who agrees to listen to a pitch is more likely to buy the product, thanks to the phenomenon.

The correct answer is foot-in-the-door phenomenon.

This means that if a person agrees to comply with a small favor, they are likely to do something more as well. So, these people will listen to the telemarketers' pitches, which means that they might even buy the product afterwards. 

Explanation:

answer; negative punishment;