billing me for something that I was not aware off

I bought a ring for my wife before Christmas (19-12-2015).She got it on Christmas day.she had it for less than a month and some diamonds fell out so I went to the store on 21-01-2016 to have it fixed.so the lady took it and said don't worry ill get it fixed up in no time.(Annastacia Basson) called me on the 17th of Feb. to collect and when I got there they wanted money for the repairs. They did not tell me that I was going to pay for it and it was not our fault that the diamonds fell out. They recon us that it could have been damaged by my wife and that is when the diamonds fell out. I ASKED THEM IF THE EVALUATED IT FOR DAMAGE AND THE ANSWER WAS NO. I promise u that it was not my wife's fault. It is simply poor quality I think. Can u please help with this. they must either give my money back or give us the ring. I am not going to pay for something that is not my fault. And if I knew that they were going to charge me I would not have given it in. I would have came to u.