STOCK ADVERTISED NOT AVAILABLE

I recently bought a printer from Game in Mossel Bay only to find that is not printing. I took it back the next day so that they can check wat the problem might be. While waiting for them I noticed on their latest weekly leaflet of promotions starting on 1 January 2020 that they offer a HP as well as a Canon cordless printer on promotion. Upon asking them whether i can exchange the printer I bought for the HP printer I was informed that do not have stock of the printer as well as of the Canon printer as advertised. This is quite unacceptable that they did not have stock on the first day of the promotion. How do they justify that? It is clear that provision was not made by the responsible person/s that the branch has the necessary stock available as advertised. I would like to hear from Game in this regard.