First time poster here. Im halfway through a trip that goes PHX-DFW-LIR (completed) but on the same itinerary is LIR-MIA-PHX. This was booked with Avios though BA on AA metal. We want to upgrade to business/first using out Avios on the MIA-PHX leg using more Avios. Is this possible or would we have to cancel and rebook? If canceling is the only option what is the penalty? Our flight is in 5 days.