I had this happen with Hotels.com where they presented an 800 number for a hotel -- the person answering the call presented himself as the Hotel's registration desk. The entire time they are telling me this and that corporate discount code isnt available. Until I asked some key question and realized they were a 3rd party trying to book you at top-rates.

I NEVER use Hotels.com for this reason, it is meant to extract as much as possible and take away the pricing power from the hotel.