Very Dissatisfied with Incorrect Price Advertised in store

On Sat 22 Dec 18 I went into Pep Stores in the main road in Vredenburg to purchase an Open View HD decoder. Advertised where all the decoder boxes were displayed the price of R399 was clearly visible ( pic to prove this). When I eventually got to the service point I was told that the decoder was actually R499 and not R399 as advertised. This infuriated me as the excuse I was given is that the store is still waiting on the new flash card. When I spoke to the (I think the manager) Randall he told me that I could not purchase the decoder for the advertised price as the serial number would not register and he would go and remove the old price now. I informed him that it was too late and it should have been removed when the price change became effective. I told him I was not satisfied with the explanation given to which his response was: "Mnr moet maar doen wat meneer wil, ek sal wag on te hoor wat PEP daaroor te sê het." (English translation: " Sir, you do what you want to and I'll wait to hear from Pep Stores. I've just spoken to Mr. Carl Smalberger the accredited installer and he had the exact same incident approx two weeks ago in the very same store and only after speaking to the area manager, whom the store called at Mr. Smalberger's request was the decoder sold to him at the advertised price. For the advert still to be up there after two weeks is in my opinion gross incompetence and I feel I had to pay the advertised price.