Typically these guys will use the same prerecorded message for all phone calls. I'll record one of them when it's convenient for me, then just note every phone number and time of day I receive another call with the same message. The messages are very distinct so it's not hard to keep track. The hardest part is having a note taking system that's truly portable as these calls come at the worst possible times.

The first few times they call, I'll ask to be placed on the do not call list (and record that fact in my notes as well). Of course, they'll continue to call... so then it's on to social engineer the name of the company or beneficiary company (if a lead generator is calling you rather than the company itself).

Once I've figured out the name of the company, then I have to basically do the whole thing in reverse: I find a "legitimate" number for the company (off the website, whatever) and get a customer service associate to read off my fake customer information back to me.

It's important to keep receipts. The attorneys for these companies don't give up easily. They'll come up with all sorts of excuses - we don't make outgoing calls, its not us (OK then how did I get your company name?); how do you know it's XYZ company? (because Bob gave me the name when I received the call); how do you know that someone didn't falsely give our company name to defame us? (because I called the number for XYZ and Dave was able to look up my "customer" record)

Once you show that you have receipts and you're serious, they generally fold very quickly.