That's the reason why these people can continue doing this scam as they know FBI/police are too preoccupied with other more persistent issues. IT's up to us to do something, can someone or some technology bombard their phone numbers with automated phone calls, much like computer virus? Just wondering.
From a different number, have attorney call and state "this is xxxx, counsel for Ms. Xxxx and I'm returning your call to my client." They'll ask if you're phoning from the same number or what was the number that was called. "I'm not giving you my clients number, this is her attorney." Click, they'll hang up on you and block you from phoning back. Just a little of their own medicine.