Flipkart — No refund policy on roti maker even after no ISI mark

I have been purchasing goods from Flipkart since several years. I am a premium plus member. I recently purchased purchased a roti maker from Flipkart. This was my second roti maker. But I am utterly disappointed by the service of the roti maker. Primarily, the roti maker lacks safety measures like ISI mark.
Secondly, the finishing of the chapatti is very pathetic.
I want to return this product and get the refund. But unfortunately, there is no refund option. Only replacement option is there.
Despite complaining several times to the Flipkart executive they are arranging replacement for my product.
I told them that I want refund but then also they are doing replacement. If the product is intact with price tags and original packaging, I don't understand why the seller is denying refund. Will the product get ISI mark after replacement?Why will I take the same product again which is full of cons.
Despite complaining thrice, no action is taken yet. I am really disappointed by the service provided by Flipkart to its plus members. I swear that I won't order anything from Flipkart in the future if Flipkart doesn't address my problem immediately.
I shall be grateful if Flipkart arranges some provision for refund .
My phone number is *[protected]*.