Andriyko

You can ask to be moved to a flight with F availability or you can ask for a full refund and buy a new ticket. if you are on a through fare, there will be no fare difference as in the absence of the required booking classes in the premium cabin a full fare economy booking class can be used (Y). The through fare would not have been different had Y been booked originally. if you are not on a through fare and by 'Y' you mean the cabin rather than the booking class, there may be a refund of the fare difference should you accept the rebooking.