Originally I was on AA 6078 operated on a A319 in F.
I think their schedule change was a downgrade to E75 which reduced the number of F seats. The flight time did NOT Change. They automatically put me on the next flight 2+hrs later. I called back immediately seeking my option. I requested to go to SJC instead. The rep sought an over-ride to get me on the flight to SJC but it was denied. I waited 48 hrs and it was still pending.
So 24 hrs ago I inquired and learned my routing to SJC was denied. After locating my original flight was still available I asked to be put back on my original flight. The rep agreed and I waited. I got an email seeking my attention earlier today. I called asking what the problem was. I was told I coudln't get into F and I had to fly out on the next flight.
I had to HUCA a few more times to get myself back in ECONOMY despite the fact that I was ORIGINALLY ticketed in F. I did manage to muster a $100 voucher.

What i do not like are these agents confirming these approved change requests only to find out it would get DENIED at the ticketing stage. I would rather these agents tell me what is and is not possible when I seek them than anxiously wait on what they had promised.