Reebok Shoes I Bought From Trendyol Have a Collapsed Heel After Only 4 Months

I bought a pair of Reebok shoes from Trendyol, and despite only wearing them a couple of times each month, the heel of the right shoe caved in after just 4 months. I returned the shoes for a replacement, but even though they were under warranty, they sent them back claiming it wasn’t a manufacturing defect and said it was a user error. This is the first time I've run into this problem with any shoes I've had before. I’m looking for either a replacement or a complete refund for this defective product. It's really annoying to get this kind of reply for something that's obviously broken. I hope Trendyol and Reebok step up and sort this out.