Worst company ever

Pick'nPay had a special on Lip Ice Assorted 4.9g Buy 3 and get 2 FREE Special was valid from 25 October till 7 November 2021 I went to the Pick' n Pay in ***unda mall they did not have stock of the spearmint flavor and they also did not have alot of stock on the Lip Ice they gave me a rain check on 31 October 2021 and I went back on 18 December coz no one has gotten back to me regarding the stock they had to get me they gave me another rain check coz they still didn't have the spearmint flavor and they said I can go to ANY Pick'nPay store to get the product today 27 December 2021 I went to Pick'nPay Centurion Lifestyle Center and they had lots of the one's I want but they said I am not allowed to use my rain check in their store I need to go back to the store I got it from coz they never had them on special and the pamflet soen not show one store only, and I think that's unacceptable and bad customer service from Pick'nPay I can't believe I HAVE to give them a star rating coz they don't deserve it at all. How do you advertise something you don't have stock of and don't order the products and get back to a customer and how does another store refuse to help a paying customer. Pick'nPay is really the worst EVER