Priceline.com priceline First Class tickets not honored by Airline Carrier norwalk, Connecticut

Never again will I use this company.  Purchased a First Class ticket through Priceline but it appears that first class designations are not always honored by the carrier (Delta), according to Delta Priceline first class tickets are coded as coach fares with possibility of an upgrades.  

During my layover in ATL, with preprinted first class seat assignment in hand,  I was told by Delta (the carrier) that I actually paid a first class fare for domestic coach seat and was subsequently down graded to a coach seat.  Customer service gave me the typical runaround,  after the sixth phone call over a four week period to priceline customer service, I was instructed to fax my reservation itinerary and boarding passes for review on three occasions and i'm still getting the shaft by Priceline.   Can they get away with false advertisement on their web site ?   Delta airline ,were a complete disappointment also...  with itinerary and purchase reciepts and pre-printed boarding pass in hand all they could offer me was the advice of this is what I get for not booking with Delta directly.

Never again will I use priceline or Delta.