Dishonest marketing

During December Guess ran a promotion whereby if a customer made a purchase of R1000 or more, the customer received a free backpack. I purchased a handbag for R1100. After the purchase was completed and I enquired about the backpack, I was told that there was no backpacks in stock and therefore they can't honour the promotion. This is false marketing, as the promotion poster was all over the store. After I brought it to their attention, they promised to try and get a bag in the new year. I have followed up with the manager, Brian, and he keeps saying that he is still waiting. It's now more than 2 months.