You should be able to switch rooms within the same category at any point in time with no repricing.Technically, I don't think it matters if there's another room in your current category. If the price today is higher than it was when you booked, policy is you pay the difference, even if moving to a new room in the same category. Of course you could get pixie dusted/supervisory override, but that would be the exception. Same thing moving to a lower category-you're still subject to the fare as it is the day you want to make the change.