Just cleared the old list of Caller ID missed calls on my panasonic phone, and the ID actually showed TAX REFUND SCAM - pretty hilarious, but our Boulder Colo. news and police announced this phone scam about a week ago, so they got the word out just about when these guys must have been calling. A few who did answer got the heavy-accented hard line, regarding owed taxes, threats, and demand for immediate credit card payment over the phone. The assessment was the number is likely spoofed, so was from out of the country in reality.
 They also were SPOOFING the Boulder Police non-emergency number, so that showed up on caller IDs locally!
This proves that you can never trust/believe the apparent number has anything to do with the actual source or even country of origin. Using a call-block system would then block actual calls from that police line, should that unlikely event occur, so the insidious nature of phone-scamming just expands.
Be Careful Out There - no level of paranoia is unwarranted.