zechuan gong

Hi everyone, I am a UK resident and bought an LV bag in France. When crossing customs I paid import VAT (20%) for that purchase legally. But when I exchanged the bag in an LV retail in New Bond Street London, they refused to recognise the import VAT paid (even though I showed the receipt and proved my legal VAT payment on customs), which should top up to the value of this purchase. They only acknowledged the value excluding 20% VAT during this goods exchange. This led to a double charge of 20% VAT, approx. 400 pounds on me, contrary to the principles of fair taxation and I feel I was mistreated and also charged unfairly as a customer. Can the HMRC do anything about this case of unfair double VAT charge? I wanna show this case to you and hope can get some help or feedback. zechuan