I wanted to share a positive experience since I was pretty dejected after reading this thread. I had an aircraft change that led to a downgrade from F to J (773 to 772) later in the year. I called several times and mostly got the standard ‘you must pay the fare difference for a different routing’. I politely said I would check into my schedule and get back to them. On the 4th call I finally felt like I had purchased a F ticket! Extremely nice, polite, and helpful agent changed my ticket routing through SFO instead of SEA - no up fare. This yet again proves that if you don’t like the first response (or three) HUCA may eventually get the desired result.