I've had a few of these calls and take the opportunity to screw with them and waste their time.  I put my headset on then continue doing whatever else I was up to while playing the fool and pretending I'm having all kinds of problems.  The last time I managed to drag him along for a good fourty minutes while I was fiddling in my garage.  When he asked what the noise was in the background I told him I was working on the motor of my vintage sports car and had been playing him all that time.  I mentioned that it was also being recorded (it wasn't) and that I'd be posting it on the net to show how pathetic he was, and that most of the world's population was much too smart to be taken in by their 'kiddee-scripts'.  He hung up quickly and I've never heard back.  Here's a group of folks playing with the 419 Nigerian scammers,  http://ebolamonkeyman.com/