Don't call them. If you call they'll know you listened and that makes you a target for more scams, more calls.
They are probably using a spoofed number or a VOIP number. The call is really coming from outside the US.
Telephone scamming is not high priority with law enforcement. The few scammers in the US know that. They move often and law enforcement doesn't have time to track them down.
I have my fax answer calls on my land line. I mainly have it for outbound local calls and sending faxes but it makes a great shield for these kinds of calls of which I just received one. I bet they love listening to my fax.
I got "the" call today and I was short and curt so the gal didn't even say anything- hung up on me. Well.... I had some down time- so I messed with them back. I spent about 20 minutes calling them! Several times it said the call wouldn't go through, but on several attempts- they actually answered and put me on hold music. It was sure fun bugging them for a change.