Amazon .in - Provide me defective computer system

I was ordered on computer system named "(Renewed) Dell Optiplex **** **-inch (**.** cm) Desktop ( Core i*-**** * GB *TB HDD Windows ** Pro MS Office), Black" on ** Jul, **** *:** PM from www.amazon.in website and i got product delivery on ** Aug, **** and on the item detail page at website it is mentioned that product is under * days replacement and backed by a *-month seller warranty program(Seller will repair your product or will provide a replacement or refund within * months of your receipt in case the product turns out to be defective within warranty period.) and suddenly cpu stopped working on *-Sep so i contacted with the amazon customer team on the same day and they told me that replacement time is over for this product, you need to contact with the seller and they provide me one chat window on their website, where i communicate with the seller and seller also response me there and the seller was sent one technician to my home to check the cpu on *-Sep and after checking the system he told us that they will pickup the system and repair at their warehouse and send us back so they picked up the system on **-Sep and after repairing i got it back on *-Oct. After receiving the system on *-Oct, i checked the cpu but it is still not working so i again contacted again with the seller and amazon customer service and ask for a refund but they denied for refund and told me that seller will again pick up the system and provide you after repairing. I am not happy with the services they provided to me, they wasted my complete month and again provide me defective cpu. So please help me out in this situation.