>Yep, it was a cheap prepaid card from an Asian grocery store, so it just deducted the connection fee + minutes. I can't remember the cost, but it was likely less than a dollar for the call. I guess if you're hijacking hundreds of calls an hour though, it's a big business.

I wonder how dodgy these phone card companies actually are. You could target a specific demographic and then mess with any calls to places they're unlikely to dial.

Say you were doing it and selling the cards in British corner shops. The customers are most likely going to be calling Eastern Europe and South Asia. They're probably not going to be making many calls to the US, so you can mess with some percentage of those.