I also wonder if going straight to Bianchi might help - tell them that their dealer ordered too small a size for you, causing you a lot of physical problems and maybe they would actually let you send the frame back. And tell them that the original dealer has not really been helpful or knowledgable about your purchase, so you are working with another shop. It is worth a try, anyway.

My hubby bought me my road bike and thought he was doing the right thing by ordering me a very small frame. After riding it for about two years, I thought things were ok, but then I went and got a pro-fitting. And he was shocked that I was doing as well on this small frame as I was, since it was too small for me. But he did some headset, stem, handlebar and seat adjustments, making it work for me (a good bike shop can do that). But since you just bought the bike based on what the Bianchi dealer told you, I would think that Bianchi should know-