Poor quality

My fiance bought me a ring at this store in gateway mall Durban, within 5 months the rose gold coat is wearing of. I went to the store yesterday and I was told that it was because of my negligence. I then asked the manager to explain, she said it was because of soap I use to bath. I then said that my granny got married with a ring of 150 rand and it is still in good shape her response was that then my grandma ring is of better quality . since my ring cost more then a R1000 but it has a quality of a ring which cost R150. Well she gave me an email address to use to contact head office I did send an email but nothing is happening.