Bad customer service

I went to the store on 06/09 to enquire about a laptop prices. The sales lady told me the specific deal I was asking about was only on promotion until that day. She took my details and said she will contact me if it goes on promotion again. She phoned me on 10/09 to inform me that the same laptop package is on sale for R4299. I went to the store on Sunday 13/09 and the same sales person completed the transaction for me. I paid the full amount and was told to wait at the security desk. Minutes later the manager came to me and said that there was a mistake with the price that was displayed with the laptop combo I wanted and that the actual price is R5399! She said that she doesn't know how it happened but that she cannot give it to me at the displayed price, however she will give me R150 off the R5399. I said that I'll rather take my money back, with wich there was also an issue because I used a cheque card. I was then informed that the refund will take 5 or 6 days. I fail to understand how they can have a display price on a item for 4 days without noticing it is incorrect and then refuse to sell it at the displayed price which was also given to me telephonically by the sales staff!