this year I'm switching to BAEX from AAdvantage,
I recently took a flight I book last year, forgot to change the FF# on the BP so it credited to AA,

I called AA and asked them to return the miles and point earned, no problem,

After that I did a retro claim on the BA website, but it was rejected after 10 days "This is because our records show that you have already been awarded points for this flight on another frequent flyer programme"

The flight was with CX and I can't claim it again online on BA, what can I do now?