False Advertising and POOR Servive

I went to CNA in Eastgate Mall on Saturday, November 25th at around 10 AM. CNA promoted a special on a PS4 500GB with 3 games and 3 Month PS4 membership for R4000.00, I was interested in this deal, but one the staff said they had no stock of this item and suggested an Xbox One S 1TB + an extra remote for R4500.00 which I was more than happy to spend the extra R500 on. On paying they said their system is offline and I can't use my account, I told the staff that I just paid my account next door at Edgars active, and the staff member suggested I go purchase a voucher and come back and use the voucher as this will work. I went to purchase a voucher and when I got back to CNA, the staff member sold me the item at R500,00 more even tho he committed to give it to me at the pre advertised price of R4500.00 and not R5000.00 without the extra's I failed to understand how something can be advertised at one price and then 5 minutes later at another without any prior warning. as this is a clear violation of the CPA, considered as false advertising.

I would love an explanation, but as the store is unwilling to assist with any queries I would recommend to avoid CNA Eastgate Mall at all cost as they sell false expectations