Flipkart — To return product from flipkart company

I’ve ordered a product(Puma Shoes Zod Runner), Size 8 using flipkart service on 2nd October but somehow size that I order didn’t fit me proper and then I made a return/replace request but at that time flipkart deliver agent asks me for looptag number which I didn’t receive with product from flipkart itself.
And now I’m requesting to replace that product with 9 number, they are nor responding properly and they ask me to made refund instead of replacement, even after option and size availability