I have a hard time searching for a good answer before calling chase. Closest was this thread:

http://www.flyertalk.com/forum/unite...dit-cards.html

But I was wondering if you could change between co-branded cards. That is, the Chase United to maybe a Hyatt? I know you can do a pc between the same brand, and you can't do it from a Chase co-brand to a Chase card (unless Chase forces it)