I have AONE3 trip coming. The issuing agent is BA as my first flight is with BA. I like to change one of my segment ( business )HKG-KUL from MH earlier flight to CX J on a later flight specifically CX725 on the same day. However that flight is not showing any D availability when I called BA to change even though it is available on CX website albeit as J fare. Since I am on an AONE3 , would I be allowed to book/change.