I understand OP's frustration because it is annoying being told "contact your bank" when the problem is an error on the merchant's back end.
OP is quite right to inform AF of the error. Maybe if more customers did that, the issue would get the attention it deserves, because customers do have a choice and the airline stands to lose revenue over this. Needless to say, having to call the platinum line every time is not a reasonable option. (And in fact not even an option at all for the vast majority of pax)