> it feels like the same approach as those people who tell you gleeful stories of how they kept a phone spammer on a call for 45 minutes: "That'll teach 'em, ha ha!" Do these types of techniques really work? I’m not convinced.

In 2000s there was some company in Russia selling English courses. It spammed so much, that people were really pissed off. To make long story short, the company disappeared from a public space when Golden Telecom joined the party of retaliatory "spam" calls and make computer to call the company using Golden Telecom modem pool.

So, yeah, you kinda can achieve something in this way, but to make sure you should lease a modem pool for that.