The scammers use voice over IP lines (e.g. magicjack (Ymax corporation)). This is against these companys' terms of use and can lead to termination of their contract. However only law enforcement can initiate the contact if you yourself are not a customer. Therefore, report it also to your local law enforcement agency. Ultimately this is a case for the FBI legal attache in Islamabad or Delhi. If you are really annoyed: call or write to your representative in Congress. As these scams happen all over the country maybe this will trigger a reaction (and the NSA can finally be a force for good).
7/15/14 received a call from Criminal Investigation Department - machine was recording message when I picked up the phone and the foreigner would not speak to me but hung up the line... I called the number back only to receive a foreign voice which said to leave message, which I did not. AND in calling my local law enforcement... they did come out to write a report, thanks!
Received call from 202-239-2026 on 7-16-14. Called back and was told there was some sort of 'tax fraud' filed against me; was told they were from the IRS/Criminal Investigation; difficult to get specific information; when I asked if they were calling from Pakistan, he said "no", when I then asked if they were calling from India, he hung up on me. Don't know if I should call the police.... I did NOT give them any information.
I also received a message from this number. Could barely understand the message (ESL). Something about a criminal investigation and IRS tax fraud, etc. etc. Complete scam.