Flipkart — I am complaining about flipkart as I got a refurbished product and was not getting my refund.

I ordered a phone [ Samsung Galaxy A52 s, 8gb variant black colour] from Flipkart on 13th April 2022. I recieved my product on 15th April 2022. The packing of the product was sealed but I don't know if it was authentic because when I opened the phone it was sealed I saw that the phone didn't require any configuration. Later I also saw that there were messages on the phone from 28th of March and one call is also place from that phone on 28th March only. I informed flipkart immediately and asked for replacement to which they declined saying the seller doesn't have replacement. To inform you sir I was promised 7days replacement policy from Flipkart but I didn't get it. Anyhow I accepted it and asked for return and refund instead and shared pictures with them. Again flipkart rejected my return request as the seller said the product packaging was intact.
I repeatedly told flipkart that the seller is fraud but I think Flipkart is more helpful towards the seller than their plus member customers who bought all her phones from Flipkart till date.

Sir, the plan basically is they will reject my request everytime and then my return period will get over and I won't be able to do much. So, yesterday night I contacted Samsung customer care to know the activation date of my phone. They asked me the serial number of the phone and I got to know sir that the phone was activated on '31st of December 2021' . In shock I started gathering proofs. I contacted Samsung again. They asked me to file a case against flipkart and the seller. I want my refund from Flipkart so that I can purchase my phone offline sir.I don't have a spare phone and it's getting really difficult to function without a phone.
You are my only hope sir. I worked really hard for the money and with that money I bought the phone so that I can study. Kindly help me with this sir. I shall be eternally grateful.

Below I'm attaching all the documents and pictures: invoice I received from Flipkart and everything.

Awaiting justice.

Sincerely,
Sanchari Ganguly
[protected]@gmail.com.