Fare Difference Math When Changing Ticket
 

I booked a flight on AA where the cost for the initial ticket in O class is $680. When I called customer service to change the date of my flight (for the same routing) the fare difference they quoted was much different from the price I could buy a new ticket for that routing on the newly proposed dates. For the adjusted date for the same itinerary I found flights on AA.com similar to my original ticket for $707. The agent said the fare difference is $167 rather than $27 (in addition to the change fee of course). Do they have some creative math when re-pricing tickets or should the fare difference really be $27 in this case?

Could be availability changed in the moments between pricing the itinerary online and calling, could be agent was ignoring fares available in a different booking class, could be the lowest fare was a basic economy fare and was ignored...try calling again and/or asking "I see a fare of X amount online, why can I not book at that price?"

Thanks for the feedback. I called again and they were able to see what I was seeing on AA.com. Unfortunately at this point the fare had in fact gone up higher still.