they claim to be  the  federal marshal office and tell me i didn't show for jury duty and now I am a fugitive until I pay $900 in misdemenor fees.  They want me to pay cash for a prepaid card at the grocery store and then give them the numbers under the metalic seal over the phone. (which by the way gives them the cash immediately)
Ya right.  The clerk at the store said she had several people come in this week with the same story...One man lost $4000

Report them:  See:  http://www.consumer.ftc.gov/articles/0048-government-imposter-scams