Complain on what basis? If you wish to get the platinum card, then did you submit proper income documents?

in that case, you might wanna to consider writing an appeal? bear in mind, changing the current gold to plat will incure another GST RM50.

-Always use Amex (if possible), on weekends because outlet that accept Amex is lesser, and got 5% and 5x TP, regardless of category.
-always use Amex on weekdays (if possible) if it's not the 4 categories for ocbc, coz Amex give 5x TP = 2.5%, ocbc only 1%
-on weekdays, if it's under ocbc 4 categories, use ocbc.
-utilities bill, always pay with ocbc (even cukai tanah has 5%), except for telco payment, if u always go shopping mall and willing to queue awhile at telco centre or outlet to pay with Amex.

Lastly, use common sense. Takkan rebate cap Sudah full for either card u still use the above rules rigidly.