Flipkart — Baby diaper wrong size delivered and not accepting return or exchange

I have ordered xxl size diaper but Flipkart delivered L size, since then 20days already passed and i am continuously requesting to return the product but Flipkart only giving false commitment and their fraud wishmaster are cancelling the return by putting remarks that product is damage but no one till now came for pickup, then how they no that product is damage??
The product is under essential catagory, then how this type of negligence and fraud act acceptable??