Amazfit Denied Warranty Coverage

I sent my Amazfit watch to the service center because there was a problem that was covered by the warranty. They gave a diagnosis report for either replacing the item or getting a refund. Unfortunately, no refund or replacement was processed. They are adamant that I should go to the place where I bought it and present the report. However, the seller failed to provide the warranty, therefore it is their responsibility to process the refund. However, they did not. In the end, I didn't receive any compensation for my loss. I had no luck in getting my message across. I asked for my defective watch to be returned, but they declined.