TRUWORTHS GALLERIA

I had purchased A dress at from Truworths online, it went on Sale, it was R719. I collected the dress during the course of this week, actually it was on Monday the 11th, that's the day, it arrived at The store for collection at Bluff. The dress was abit small, and i checked online to see where it was availability for a 34 and that was Galleria. Yesterday i went into Truworths Galleria just to swop the sizes of the dress from a 32 to a 34, the cashier at the counter credits the amount for R719 and recharges for R799. So i explain that was not the price and im just changing a sizes, i was then told the sale is over n if thats the price i want it at i should have exchanged it while the sale was on! How exactly am i supposed to do that when the dress was online? By the time is arrived at the store for collection the sale was over. I work during the couse of the week! Yesterday was the first chance i got and that's the reponse i get for taking the same dress just another size! Its completely unacceptable! I have purchased online many times at other stores and exchanged a size instore as cuts and sizes differ but i was never told something that outrageous.