Sterns complaint

I'm so disappointed in sterns promenade. My husband bought a 3 piece wedding set end of June. I started to wear the ring in July and noticed it made my finger itchy but didn't take it back just yet I never wore it again until August this time it made a rash. End of August I took the ring in to check if the can do something with the ring only to hear back from them in mid September. I took the ring back because the thing they wanted to do was to expensive. I wore the ring again whice made my finger full of blisters and took the ring back to the shop. Only to hear back from them in October to tell me they can't take the ring back or credit it I have to keep the ring. I asked the area manager how can I pay for something I can't wear and his response were well than you mustn't use your ring in water but they can see that ring is still new. The other day he send me a message saying the send the ring for testing and there is nothing wrong with the ring. I went to the doctor with the finger and he confirm its a allergic reaction. Still they say I must collect the ring. I even asked to exchange it for something in the same price range but the manager refused. I'm frustrated with this shop