I've been messing with these guys for months. Every now and then I call them from a made up number, (Google App Caller ID Faker) and claim I got a call from them and am returning the call. I let them do their intro scam thing, then just ask them how to pay, (most of the time it's a money order). If they want a bank transfer I claim I don't have a bank account etc. So they have to accept a western union money transfer. I say I have to goto the post office to send it and will call them back.... after I hang up I watch an episode of my favorite show, then call back with some made up crap on how they can get the money.

Eventually they catch on that I haven't sent anything... so I say something to the effect... "Well you are a fake IRS agent so I figured I'd send you a fake money order." They really get pissed at that point and I hang up.