My tip for getting under their skin: sincerely try to persuade them that they deserve a better job than the shitty, exploitative thing they're going. They are prepared for yelling, but not so prepared for compassion and honesty.
I've also had some luck opening with, "Does your family know that you lie to people for money?" That can be a good lead-in to suggesting they do something actually worthwhile.
In high school I was prodded to get a job, so I looked in the paper, applied for a bunch of things, and eventually got one. It was a company that did telephone fundraising for charities, which at 17 seemed ok by me.
Very gradually I learned that it was run by scoundrels, and that only about 15% of the money raised actually made it to the charity in question. The work was awful, but I stuck with it because that's what you do with jobs. It was the realization that I was basically helping scam artists take money from big-hearted, too-trusting people that got me to quit.
Conscience isn't some fixed thing; it's a skill you learn, a habit of ongoing evaluation. If I can wake just one of these people up so that they, like me, go and get a job that isn't net harmful to society, I'll consider my time well spent.
My tip for getting under their skin: sincerely try to persuade them that they deserve a better job than the shitty, exploitative thing they're going. They are prepared for yelling, but not so prepared for compassion and honesty.
They'll just hang up as soon as they know you aren't a mark. I've tried everything, with these folks.
My goal isn't strictly to help them; my goal is to get them to stop being paid by criminals to waste everybody's time (and possibly steal their money).
I've also had some luck opening with, "Does your family know that you lie to people for money?" That can be a good lead-in to suggesting they do something actually worthwhile.