Last year, we lost our seat assignments when USAirways changed our flight. Same story about don't worry, they hold back seats to get assignment at check in. Well, I let them know that I had paid for a flight which gave me seat assignments(we were trying to keep two groups together, total of 6 of persons) and that I felt that removing my seat assignments and risking people being separated was a breach of the agreement under which I had purchased the original tickets and that I expected to be put on a flight on which we could have seat assignments now ! Well, the girl was not particularily cheerful, but she found a flight on which she could give us seat assignments and keep our group together. The times were not all that different either. I guess some of the agents are more willing to work with you than others. I would keep callilng until you find someone who will help you .