general problems of the 2005 Dodge Dakota

I bought a new 2005 Dodge Dakota from heritage Dodge (reistertown MD)partially because of the gas milage advertised at 16mpg city/20mpg highway. I have been monitoring the mpg and found out that I am getting 9 miles per gallon no matter where I drive(city or highway). This is a mid-size truck and should be getting better mpg. I have contacted my salesperson(tim) and he referred me to call rob schmidt(service dept. ???) who has not returned any of my numerous phone calls to check on this problem. My salesperson(tim) told my wife on the phone that the truck should be getting better milage. I would like to know how Dodge can advertise on the sticker these false miles per gallon when they know they are absolutely false. Tom.