Before and after buying, you can ask the clerk whether our store supports making up the difference and exchanging old ones for new ones.

Because the platinum necklace you bought, whether your necklace is 18K gold or platinum, is not pure gold. If it is a replacement, there must be a price gap. Usually, gold with the same value can be replaced according to the recovery price * gold weight, or gold ornaments with higher price can be purchased by making up the difference.