Return Policies for Goods in France

Last week, an unpleasant incident occurred in one of the luxury boutiques in Cannes. My daughter and I were looking for a dress for her graduation party and chose a Zuhair Murad model. Since it was a model from the previous collection, I inquired about the possibility of receiving an additional discount.
In the correspondence, I was informed that a 30% discount had been approved by the boutique director. The seller confirmed that the dress was reserved for me with this discount. We scheduled a second fitting and went to the boutique for the final purchase. My daughter tried on the dress, and I paid for the purchase via Apple Pay.
Later, upon checking the receipt, I discovered that instead of the promised 30% discount, only a 20% discount had been applied. The difference amounted to over 400 euros. I immediately wrote to the seller with whom I had been corresponding. In response, I was informed that the decision on the discount is made by the director, and on the day of purchase, she was not in the boutique, so the standard 20% discount was applied.
When I shared this situation, many advised me to return the dress to the store and get my money back. However, if you purchase a product directly in the store, the seller is not obliged to refund the money or accept the product back. This is the right of the specific store, not an obligation established by law.
Purchases made online operate quite differently. In this case, Article L221-18 of the Code de la consommation provides the right to withdraw from the purchase within 14 days without providing reasons.
My dispute with the boutique was not about returning the dress, but about the discrepancy in the promised discount. The correspondence with the seller confirmed the 30% discount. Since the purchase was paid for with a bank card with additional insurance coverage, I contacted the bank. The bank agreed to compensate the difference between the promised and the actually provided discount.
In France, the sales season is about to begin. Be careful and always check the final amount before payment, even if you are shopping in a well-known luxury boutique.