I hesitated calling the number as it sounded too good to be true. Did you try calling the number? How did you research it to find it was a cell? I googled it and found this and other sites.
It's a scam. They 'sell' you the tests and locations where you can get hired for DHS in America. It's the the Department of Homeland Security, it's a company that claims to help you pass the DHS tests and help you find where they are hiring.
I did not get a phone call but the job posting was recommended to me by CareerBuider.com. I did an internet search on the phone number. I know from experience that Civil Service jobs have free study materials available through libraries, etc., so this is indeed a scammer trying to separate people from their money--a particularly reprehensible person in this time of high unemployment and financial insecurity. I placed a notice documenting all of the other phone call receivers' experiences on CareerBuilder.com. Thanks for all of y'alls' diligence in watching out for scammers and unscrupulous "business" operators.