Lee Cooper — casual shoes defect

Address: Mumbai City, Maharashtra, 400092

I bought shoes through myntra 15 days back and wore it once.in one wear threads of the shoes came out. When i checked with myntra i got reply stating that it is not a manufacturing defect so they can't replace it. I did not understand how this is not manufacturing defect. If stitches were done properly this shouldn't have come out.

Please let me know way forward on this.