Screen black, wont turn on, please help!

I bought a Samsung Galaxy A50 from BackMarket (dont ever buy from them its a scam!!!)

Anyway, literally as soon as I turned the phone on for the first time after unboxing I knew the screen was broken somehow.

The colors were all off, everything turned either neon-ish or white when the brightness was all the way up. Over a span of maybe 3 days the phone developed a yellow, green, blue, and black spot on the side that slowly took over the entire screen. I'm assuming this means they sent me a phone with a broken OLED?

The original seller refuses to speak to me, Backmarkets phone doesn't even exist, and the ‘representative’ refused to refund, repair, or replace the phone even though it was broken when I got it.

Is there anywhere I can take it? Can it be fixed? I just spent almost $300 for a work phone (not including the price for a case) that I never even got to use and its been months since Ive had my own phone, I dont have the money to buy another one but I feel like its going to be just as expensive to buy a new one as it would be to fix it….

Someone help please :(