Sterns ****py rings

I laybyed my wife's wedding ring in December 2018

My last payment was March 2019 I got married on the 28th September 2019,only then my wife started wearing the ring obviously

In December 2019, after 2 months of wearing the ring, the 2 pieces of rose gold fell off including one of the little stones

I went to the store in parow, told them that I unfortunately don't have the slip but they should have a copy, which they couldn produce at the time

They said that the 6 months have passed so I Wil have to pay to have it fix

Gues what, the ring costed R1200, but R800 to fix

My concern is that how can a ring break that easily after 2 months of wearing it, a d then all they say is that it's customer negligence or normal wear and tear

Why can't they check the ring and see for product defects or something