iPhone 7 + Cover purchased - Poor quality

We purchased a silicone matt black cover from the iStore in Eastgate Johannesburg on the 8th of September and it has started fading in certain areas on the sides as well as a piece that has come off.. We purchased two, 1 for an iPhone 7 and this one. The cover for the Iphone 7 is still in good condition but the the one for the iPhone 7 Plus is not. We went to the store last Saturday the 4th of November with the proof of purchase to get the cover replaced. The store manager lady just took our details and said they would call us back to let us know what they are going to do about it. On Friday I phone the main number and had to wait for the Eastgate branch to call me back. I got a call yesterday morning to ask what the query was which I explained again and was told they would call me back. But basically, no one is really interested in resolving this as we are not being contacted or given feedback!!