Return service in Apple city creek center

I bought two iPhone 12 in Apple city creek center on October 1st, 2022, and I found one of them can't be turned on. I brought this one to request a replacement on October 3rd, 2022 in the Apple store, but the manager told me they can't return it because it is a modified one. They claimed they found the extra screws inside the cell phone after opening it. How can they sell the modified and broken one to me and refuse to return it?