Flipkart — MI 11 Lite phone

I purchased a "Mi 11 Lite" phone from flipkart in exchange of my old phone. It cost me Rs.21999. I paid Rs.15149 in cash and exchanged my phone for 6950.
The display-panel was defective, it was showing green colour pixels in the bottom half of the screen. But this issue was only visible in black background. So I requested for refund and the technician (Jeetendra Singh) was assigned to check my issue on the phone.
The technician was very unprofessional. Even though he admitted that the issue is showing on black background but when he was uploading the photo of the issue, he did not captured the black background (where the phone shows the issue). Instead he captured the photo of another colour background (where the issue was not visible). I asked him to capture the black background so that my issue is shown in the app, but he refused. So my return request got rejected due to his unprofessional behaviour and his lack of knowledge.
Again I re-requested for a refund and again the same technician was assigned. I asked the customer care and they said that if the technician could not solve my issue then i will be refunded. But he neither solved my issue nor he passed my refund request. All he had to do was to capture the screen where the issue was shown but he refused. Even though he admitted that there is a green colour issue in black background he refused to capture the screen with black background. So my request got rejected twice.
Now I was very disturbed by this but I gave them another chance, i asked customer care to assign me some other technician who knows his work. So a new technician was assigned to check my issue, his name was'Maunoo Ram'
but when he visited me i found that he was the same person who visited me earlier i.e, 'Jeetendra singh'. When i asked him whether he is jeetendra or Maunoo ram? He told me that he is both and he will come every time even if the name is different.And he once again refused to proceed my refund request. Now i was seriously mentally disturbed.
So i complained to flipkart customer chat service, i even sent them proof of defective product but they kept leaving the chat without giving me any solution. As i realised that i will not get any solution here then i complained to the govt. consumer portal. After this flipkart's executives called me every single day and every time they asked me the same question "what is your issue with phone?" and I told them every single time, but I could not get my refund.
Then one day an executive called me and told me that I will get my refund after I upload the photo of the defective screen on the chat section. Then I uploaded it to the chat section, and once again as always, the executive left without solving my issue.
But now i had enough. I am done being mentally harassed by Flipkart services. I could not sleep at nights. I purchased this phone from my 5 Months pocket money. My patwari exams are next week and i can't continue my studies online due to this mental tension and there defective product. I have already lost my valuable time due to them. And now i am mentally not well due to flipkart, there technician and there customer services.
So now I demand my full refund + i will keep the phone too. This is very less than what they truly owe me.