Originally Posted by
dazza189
One of the underlying problems here as I see it, is that they already rebooked my folks on the BA flight at my request, and then 2 weeks later told me to phone them, so they could demand another $500. The itin is no longer viewable in my bookings so I can't actually print it out.

Had they actually reissued the ticket before contacting you? If yes, then I would def agree that the airline has no grounds to charge retrospectively
Do you have the booking reference and are you able to view it by reference?