Has been calling about fraud issue and number will not receive incoming calls. Not sure if legit or not.

yes, i think it's a hoax.  But I don't know how to report it.  I told the man to stop calling and communicate by mail only.  They still keep calling. I am going to try calling the IRS.  What have you done?

It's a scam.  Report it.

See:  http://www.irs.gov/uac/Newsroom/IRS-Warns-of-Pervasive-Telephone-Scam

Get a call blocker.  Don't pick up on numbers you don't recognize.

The number won't receive incoming calls because the number you saw in your Caller ID is spoofed. It's not the number that really called you.

There's no way to tell the number that really called but behind it are some crooks trying to scam you out of money. Don't answer these calls or try to call them back at any number. Real bill collectors and real government agencies send you notification by postal mail.

Got a message from an Agent Marvin threatening litigation. Thought it was BS. Called -- rang several times, then call failed...Then minute or two later got a call back from 202-239-6612. Traded hello three times--Then hung up. After that--still very much consider this BS, especially since googling the number, I get websites lit this instead of a legitimate organization.