Display problem

I had complaint with the camera of my laptop and I registered the complaint within the warranty period. The technician came and changed the display and motherboard with a refurbished one. And within a month my laptop started showing much worse defects. The display is not working properly and laptop is having high heat issues. It even switches off on its own now after using for a few minutes. I have called Dell customer care a number of times and I couldn’t get any satisfactory response. The warranty period is now over and they are not helping with warranty extension. I don’t know what to do now. Dell customer service is really bad. I spend pretty much amount on this laptop and it’s not in working condition now. I beg you to do something about it. I’m having worst experience with Dell here.