OnePlus - Sold defective phone by company but no compensation

I had bought one plus *pro phone from Amazon in ****. The device worked fine for the first couple weeks, but after that my phone started having issues. First the issue started with battery life, the battery would drain out unusually faster and the battery didnt last long. I gave my phone for repairing in the service center. Then after a year i updated my phone, and after that update green lines started appearing on my phone. I gave away my phone for repairing once again, but then issues started with calls, i couldn't pick up any call because the call would disconnect on its own, and even if i did sometimes manage to take up a call i couldn't hear any voice from the other side of the caller. And now on **st March, ****, when i was on call with a relative my phone suddenly switched off and wouldn't turn on no matter what i did. This happened at night, around *-* pm, which is when the service center starts closing, so i didn't have the option to visit the service center immediately, so the next day i went to repair store immediately. They told me to wait till **re March to find out what's the issue with my phone. I got the call and i found out that my phone's motherboard is damaged and i must pay for the repairing of the motherboard, which they're asking **k just for the repair. My phone's motherboard damaged without any prior indication and i never once dropped my phone, ever, or even got my phone wet. I asked the company for compensation for my loss and selling me a defective phone which had issues from the start, but the customer service refuses to listen to me. They said that they can't do anything about the damaged motherboard now and if i want my phone repaired i must pay that **k or i can take back my phone without any repairing. i always had problem with my phone since the very start of its purchase, and i mentioned this to the customer service but they said that if i had any issue i could've requested for a replacement, which is a policy they provide if something happens to their phone under ** days of purchase. But i encountered issues with my phone after ** days of purchase, so I couldn't have replaced it even after encountering so many issues. I had very important documents in my phone and now I cant retrieve it without paying such a hefty sum for a defective phone, I had lost all of my important documents and pictures.