Crocs India — Severe shoe bite and denial of return of product.(unethical behavior)

Address:

Kanpur, Uttar Pradesh, 208001

I purchased a pair of slippers (crocs) from shop named katwalk of z square mall of my city(kanpur).
i used the slippers for around 4 hours which resulted into severe shoe bite and blisters.
i immediately went to the shopkeeper to change them for which he just denied.
how do the shopkeepers expect someone to know everything about the product before hand, things like shoe bite cannot be tested as the time of trail.
what kind of customer service is this that is provided by your company crocs.