Decathlon Refused to Replace My Corength Barbell Though Domyos Is Still Reliable

I bought a barbell at Decathlon in April 2024, but it has black marks on it that show up differently when I look at it from different angles. When I called customer service to ask for help, they told me that it wasn't covered by the guarantee. The quality of the brand Corength doesn't seem to live up to my hopes. A Domyos dumbbell, on the other hand, has been in use for more than four years and still looks and works great. I'm very upset about the difference in quality and would like to ask for a change with a more dependable product, such as Domyos.