Its called screen burn-in. Sadly thrre is no way to fix this. If your warranty hasnt run out then you'll have to replace it otherwise theres nothing you can do about it. Sorry, try contacting Samsung.
Thank you! Do you know what causes it? My warranty should still be could I have only had this t.v since December and purchased an extended warranty.
It could just be wear, or if your getting a flame and heating it up. Most of the time though its because of keeping the TV at peak brightness levels (for example: constantly having a white image on full brightness).