Unreliable TV quality.

I bought a hisense tv from them recently. When they turned it on on store, the picture was fine. After taking it home the unit proved to be less than ideal. There was light leak bleading in from the edges. I had the unit for a couple of months and the issue deteriorated and became more distracting. It took some time for them to honour the warranty. They sent the technicians out who said nothing was wrong, after contacting them and explaining I wasnt happy with the unit they eventually sent another technician out, this was after I took the tv to the store and was told their technicians needed to check it. I took a afternoon off work to do this. They really took long to get the ball rolling. I managed to eventaully get a store credit and decided to go with a different tv. I went with a TCL as it got fairly good reviews. When they turned the unit on in the store, it was a black picture with some text. I took them at face value and bought the unit. Immediately when I got home I set up the tv. I noticed that the unit had some dirty screen uneven light across the screen. This is commonly known as dse. There is uneven light across the set and it looks like the tv is dirty and uneven in terms of picture output. I've had the set for 4 days and I can see the dse or dirty screen effect when I watch sports, movies and play games. The issue is very noticable when there are grey tones. It's noticable when the picture is darker. It's even noticable when the screen shows bright blues. It's a new set and the quality is terrible. What on earth are they doing ? I kow it's a cheap set and there is the so called panel lottery, but how can you sell a customer a tv that has this issue ? Two tvs and both are sub par in terms of quality ? What do I do now ? I am not happy. I expect a tv that does not have issues that distract from the viewing experience. It defeats the purpose completeley. I bought it in good faith and I got burnt twice.