Bought a TV that is not working

We bought a Hisense 65” TV that was tested at the store, packed back into the box and was sellotaped. When we got home, we saw that it had purple pixel lines showing at the bottom of the screen. We went back to the store and HIFI corporation could not account. They placed the blame on us. As the TV was being tested, the pixel lines got worse and extend to the sides of the screen. We have bought a TV that is not working.