Good, but to be sure, you may want to consider logging out of the app and logging in again. The ticket number is a cache item and can give a misleading iimpression unless you refresh the cache fully. But that said, if you call up within 24 hours of departure then yes it is under airport control and Engagement Centre staff can't help with seats, without making further telephone calls, which they normally won't do. But if you are going via a BA location in the USA they can just see available seats on Altéa and let you change them. You can also change seats in LHR when you get there.