Factory Outlet Store-Item Not Usable

I ordered a friction mount for a Garmin 350 Nuvi. The sales representative on the phone was very clear that the item would come ready to use. She said that the it would fit on to a piece that the Garmin comes with. When I received the mount, there was no way to attach the Garmin to it. I called the company to complain and they would not take responsibility for their mistake. They said I had to order another part in order to make it work. I want to return the item but they will not pay for me to ship the item back to them even though I only bought it after they assured me that it would come ready to use. I requested to speak to a supervisor and was denied access. I am very unhappy with this company and would never use them again.