Redmi - Received used and defective product and filpcat refused to return or replacement

Received used and defective power bank which is not charging its indicate charging but charging not completed. I had tried to return or replace but flipcart customer care refused to repalce or return i had requested * to * time but they had rejected. I am helpless now it showing in app your return and replace time is over my now i fill my full money is waist. Pls help
Item power bank redmi
*****mah
Date of purchase ** jan ****
Oder id OD******************