Close but not really what I said. I speculated that it is possible to do so, I didn't wonder why one couldn't. Think about who is calling you. The people working those phones aren't and never will be Kevin Mitnick. They're poorly educated, morally apathetic, have no real options, are unlikely to be employed at the same place in a few weeks anyways, and may in fact be being scammed by the people running the operation as well. People fitting that profile are prone to believing that they've gotten/will get lucky despite the evidence, see lotteries. They're basically indistinguishable from their ideal marks.

Also, yeah supervisors might be listening to the call/the call is recorded, but it would be uneconomical to monitor them all live all the time. Any attempt to turn them would hinge on their expectation that their remaining time at the gig is going to earn less than what they expect to get from you. If you can convince them that they could make $1500 now, that's a month's salary for them. If they expect to be fired tomorrow then even a chance that you're telling the truth starts looking worth it.