I just called BA, who issued my DONE4, and asked them to change my flight from JFK to HKG, CX 831, to AA 8924 (the latter being the code share number for flight 831) I will be taking this flight after having flown SFO-JFK on AA, so my previous flight is AA. He said it can't be done. Any advice? Should I have fed the code share number to the agent when I booked? (The oneworld booking tool, of course, does not list code shares.) Will AA do it? I understand if another airline touches the ticket, they have to reissue the whole thing, so I doubt they'll be enthusiastic even if able. It matters for EQM accrual to AAdvantage 2 EQM/mi on AA vs 1.5 on CX.