I thought about that and asked. We are past 24 hours, so not automatically entitled, but was told if I cancel that the same conditions will apply, and I could not just go buy another AC ticket on the same route. They would only let me use the credit on higher fare cards. As an update, after another call with Orbitz yesterday where they contacted their AC liason, I was told that the reason was that there is an agreement (with AC or UA, which is the codeshare for the last leg, is unclear) that the rebooking had to be in certain higher fare classes, which was why they would only sell me another ticket for a multiple of the same price (mine was in discount business, so that apparently left only full fare or refundable business). Incidentally, I am aware some airlines have requirements to rebook in the same fare class, but not a higher one. However, when I asked if she could tell me exactly what the rule was and what fare classes I was permitted to change my ticket to (figuring I might find a cheaper one myself if I knew what fare classes I was looking for), the Orbitz rep said she could not tell me that because that was under a confidential agreement they had with the airlines. I could only ask for a flight and they would give me a price. (In fact, getting them to tell you the fare code they were pricing at was like pulling teeth, and one agent would not tell me, but the others would when I insisted.)

To me, this higher fare code requirement is an undisclosed condition. I don't find it on the AC website, AC conditions of carriage, the Orbitz website regarding change of tickets, or the ticket email that Orbitz sent. I am thinking of making an FTC complaint against Orbitz, a DOT complaint against AC (maybe UA as well) and raise the dispute with Amex - not because I think the airline cannot make a rule like that or that I am complaining about the change fee or other limits posted online like same route or airline, but that they should have to disclose such a rule and not keep the exact terms secret from the ticketholder.

[Update: On another call, I finally had it confirmed that all the AC fare codes were P and the UA fare code was T. I want to keep those fare codes. But apparently, that is not permitted on a ticket change. But they still will not tell me what codes I could book into. But from the prices it looks like they would only change the ticket to J, C or D (AC business full flex).