Engagement ring

My fiance bought a engagement ring at sterns clearwater mall. In a week's time the diamond came loose so they replaced the ring by giving me a new one. In a months time the same happened with the second ring. So we went back and they just gave a new one again. I am currently at ring number 3 with sterns and now the ring just bends for nothing if I have to pick up a box I need to take off the ring or it bends. So we took the ring back and almost a week of giving the ring back we are still waiting on a response. I just have to say that sterns quality on rings and customer service are useless.