Punki, congratulations on standing your ground! I too got caught by surprise the first time I booked an AC codeshare. They are to be avoided like the plague. They won't upgrade you, won't let you change flights, and won't even let you in the AC airport lounge in ORD...it's run by TWA and even though I had 1K, RCC, and Amex Platinum they would not let me in. (I've since learned that it may be possible to get a pass from the AC gate agent, but who wants to stand in that line?)

Sorry you got a bad egg on the PremEx hotline... there are some good ones too as I'm sure you know.