Frontline Consumer Research Group Check Cashing Scam Trenton New Jersey

Beware of this company. I received a letter stating that I had been chosen as a Mystery Shopper. I thought it sounded too good to be true, so I called the Frontline Consumer Research Group and was told by their representative that it was a legitimate offer and a legitimate check. So I proceeded to the bank and put it in my account and waited for it to clear. I am still waiting for it to clear.
When I called them back to get a confirmation that the check was legit she gave me a huge attitude how if I was going to continue to have problems, I shouldn't work for them. She also said that no one else has had a problem with this check cashing. So now I called the bank that it was routed from and they told me there is a restriction on this account and no money will be able to be withdrawn from it.
What is the next step to take? Please let me know.

Lizerd71
Buffalo, New York
U.S.A.