Final answer:
Telemarketing is the term for making unsolicited telephone calls to gain business. It has become less effective due to technological changes such as caller ID, and changes in consumer behavior like busier schedules and a desire for privacy.
Step-by-step explanation:
Making unsolicited telephone calls to gain business, which are subject to 'no-call' restrictions, is commonly referred to as Telemarketing.
This practice has faced various challenges, including the increased use of caller ID, decreased use of landlines, and rising consumer privacy concerns, which include the use of privacy managers and preference for voicemail. Additionally, the hectic nature of personal schedules and a decreased willingness to be interviewed have also contributed to the declining efficacy of this marketing method.