VG270 rated for 165hz, black bar takes up bottom 1/3 of screen unless i drop it down to 60 hz

I've had this problem before, couldn't find anything to fix. luckily I was still under warranty so I sent it in for repair got it all back and worked great. however, when I got the monitor after having it repaired, I only used the 144Hz option because I figured using 165Hz was unstable because it says OC to 165Hz. upon receiving the monitor I used it for another few months and the problem had come back. now I'm out of my warranty, and really sick of this problem. I've called in and I'm just told there's nothing I can do because I'm out of warranty. what do I do now?