Hi everyone
I bought my RTW ticket with Cathay Pacific in Delhi, India. I'm due to fly out from Tokyo on the 30th of June to Fan Francisco through LAX with American Airlines. Something's come up and I now need to be in SF on the 27th.
I called Cathay Pacific and they told me it shouldn't be a problem, but to call AA to get it confirmed.
After ringing AA, they told me that it is impossible to fly out any earlier than the date on my ticket. However, according to their website, there are still tickets available, though only full fare seats.
Is it possible that the representative was wrong? Should I be able to change my ticket provided seats are available?

Thanks in advance