Hi,
Jewelry which your friend gave you. May be he was wearing after purchase. So instead of complain others better you check it with your friend. Sales staff when he sees the condition of jewelry may be realizes that using every day. Always before buying we have to check properly. Even if they exchange I am sure they will sell to other customer as new. That’s why many jeweler shops after purchase they never take back or exchange. It’s really good idea.may be in australia they exchange and sell second hand goods as new one.