I have an AONE5 issued by Trailfinders in London. I want to change the date of the flight from Santiago to Aukland but Trailfinders want to charge me £50 per ticket to make this change before I set off on my trip. Is this normal? American Airlines have changed their segment for me already at no charge, but QF and LanChile refuse to make changes until I set off. What are my options please?