I understand how you feel. It's not about the free gift or freebies, but the principle of the matter, that you felt cheated.
You could, and should, lodge a complaint with the manager of Chan Brothers. Whether they would entertain you would depend on their service levels and how committed they are to customer service. However, it is perfectly normal in Singapore if they were to keep to the original deal, as there is no black & white from the tour consultant. You only have his word for it.
You can continue to pester the tour consultant, but it should not cause you to not enjoy your trip. Just go for the trip at the end of the day, enjoy yourself and take some nice photos to show us at clubsnap. After all, you paid for the trip already, right?