Poor shop assistants

I purchased a pair of running shoes about a year ago. Due to heart complications, I refrained from running for a few months to aid my recovery. I started using the shoes just a month ago, and despite having only 80 to 100 km on them, they are already falling apart. When I approached the shop assistant, they acknowledged the product's defectiveness but were unwilling to assist in sending them for evaluation, citing the expiration of their standard 3/6 month return period. I want to clarify that this is not a criticism of Nike, as I have always put a considerable amount of mileage on their shoes without issues. Rather, it highlights the absolute unwillingness to attempt to send the shoes back for evaluation in this particular case.