The agent handling the change assigned me to a different car than my original assignment. Was this necessary? Couldn't I have just remained in the same car and room? I certainly would have like to stay in my original car and room assignment.
Well it's necessary in the sense that the agent cannot just change the price on the room. My understanding is that the agent must release the current room back to inventory and then request a room from the pool to get the lower price. Now, there are two ways to request a room. 1) Simply ask ARROW to supply a room from point A to B. This is the easiest and will most often result in a new room being assigned and perhaps even a new car. 2) Pull up the available inventory for the train, select the car you want, then select the room you want. This requires a bit more work on the part of the agent. It's not a lot more work, but it is more work than just telling ARROW to give you an available room for that train and city pair.
While all agents are trained in both methods, probably 95% of the time they only need to use method #1 so some forget how to do method #2. And of course some simply consider anything that requires more work, even if it is only a few keystrokes, taboo. But if all one says to an agent is "I'd like the lower price" you are most likely going to find yourself with a room & car change. One must be far more specific that you not only want the lower price, but you would really like to keep the same room.