Free bag from CI but credit miles to Delta?

Hi all,

I am currently a gold card member of China Airline, but I want to change my main program to Delta. I know that Skyteam Elite get one bag free on delta flights, but my problem is that I want to credit my miles to delta account instead CI's.

I tried to enter my skymiles account on my ticket and show them my CI's membership card when I checked in at the desk. However, they kept telling me that I can either choose to have the benefit of one bag free or my miles on skymiles account.

Any advice on that? Or this is the only way to do such thing.

Thank you very much for any input!