False adverting. NO stock

Im very dissapointed with Massmarts Empangeni Cash and Carry. They had a special ending on the 7th September for 12x 50ml Aquafresh toothpaste at R79. I did buy but not enough stock as there was 4 on the shelf. I enquired they say it will be here next week. I came today on the 7th a week later and no stock had arrived. I asked for a rain check from the manage but was refuses because of some stock control reason they said. I phoned Mtuba branch and they told me it hadnt even arrived for the duration of the promo. This is false advertising. I would like to be assisted on this please.