Jeff has a business and he's being overwhelmed with telemarketing calls from scammers. Leo says that if it's a legitimate telemarketer, he can demand they put his number on the Do Not Call List and by law, they can't call him back. Scammers, however, just don't care because they don't obey the law anyway, and call from different numbers every time. Unfortunately, there's not much Jeff can do with a business except just hang up the phone.
Could RingCentral work? Leo says it wouldn't hurt, Leo uses them, but he isn't sure it'll do much. It's a great service, though.
Another option is to use Google Voice, which enables him to route calls to voicemail. But If he doesn't know who's calling, that's rather impossible to prevent as well.
Since most are autodialers, having an interactive voice control attendant that forces the caller to press a number to speak to someone will kill the calls eventually.