Flipkart - Flipkart — received a different variant of the phone and even its not working

i ordered redmi note * pro( gold *gb, **gb ) of Rs ***** (flipkart sale price) on *th nov evening with an exchange offer of my old iphone * (****rs - ***rs as pick up charges ) by paying Rs***** with cash on delivery as my payment method
on *th nov evening, i received a rose gold variant with gold variant box (and even that phone is not defective ), i immediately contacted customer care, they suggested me to put a replacement request, and i did but the very next day (*th nov) they rejected my replacement request by saying "seller is unable to fulfill your return request" . i again put a replacement request and even called customer care over ** times , they just keep extending the time for resolution but do nothing . and today (*th nov) they told me to wait for another ** hours .

"worst customer service ever"