first the chain now the ring

1st of all ive bought a chain from them around th 22nd of december 2014 not even a month later the chain broked and whe tooked it back they send it away and fixed it not even 3 weeks after the repairs was done it broked again so whe tooked it in and talked to another lady again and wheve decided to take something else because whe dont want something that broke every second week so whe decided on a ring with the help of the lady that works there about 2 0r 3 months later one night me and my wife recognise that the small diamond isnt on the ring anymore so whe tooked it back the next day so the lady said they gonna send it away and see now whe get a response that the ring hass being fixed butt whe have to pay 300 an something rand im realy not happy with this what can i do i am really dissapointed