ISINI GEMS & JEWELLERS (PVT) LTD. - Sri Lanka

I was with my wife in this shop and I thought it would be a good idea to buy a ring. To cut a story short I purchased a 14ct white gold dress ring with a white sapphire set in the middle in a four claw white gold setting, I can't remember what I paid but I think it was about £500 sterling. I have had the ring valued for insurance purposes and I was told that the stone is NOT a sapphire but a cushion cut white topaz.....valued at £275 sterling. Don't touch this shop with a barge pole. What am I supposed to do, take the next flight out and compain ! Thats why they rip off tourists, knowing they cannot go back.