You cannot use multiple promo codes at the same time. Usually, codes are made to run alone, so the other code will not be available if you have already claimed a promotion. For instance, since the codes "hellagood" and "hellabonus" provide the same bonus, they cannot be used simultaneously. You only have one code per account. If you want to use other promotions, you can always wait for the current one to end and then claim a different bonus from the website.