Please help

I recieved a call from a consultant who advise me that he can provide me with 120 gigs of data for 399 with out a 24 month contract. I recieved a message which stats I need to make payment first to process with my order I when on there website and I find 60 gigs nite and 60 gigs day I am really afraid to make payment. I tried calling and was not able to connect anyone.