Poor craftsmanship and quality of expensive rings

Hi, Extremely disappointed. I purchased a ring for my girlfriend on the 4th of October, on the 5th of October I noticed a stone had fallen off. I called them and sent pictures, they replaced the ring on the 11th of October. I hadn't used the ring as I dis not see my gf for 2 weeks after. I gave her the ring when I saw her on Saturday (25 October). This morning she shows me a picture. The stone has fallen off on the same spot again. Expensive ring and poor workmanship on it. Very very disappointing + i paid extra for insurance.