Lies - priced incorrectly

Today the 24th May I place an order on the bottles App of 4 x Dog Food 6kgs at R26.99 each and 2 x Cat food 4kgs at R21.99 each. I pay and 10 minutes later get a message to say Dog Food out of stock. Because this has happened before I decide to call the call centre and they assure me there is NO STOCK, now I question the call centre agent and ask him why he couldn't source the item from another pnp he says there is NO STOCK.. absolute lies. I then get into my car and drive to the pnp and YES 2 x Dog Food on their shelf.. yes I have the pictures of proof of course - now why tell me there is no stock when you have 2 bags in your store. I then put 2 and 2 together that pnp or bottles realized that they have made an error on their App of the price and had to lie to a very very regular customer saying they had no stock. I will not accept this, I paid for what was advertised and I want what is due to me. Your error not mine, me as a customer played my part.