Brand new tv showing purple spots

Bought a brand new JVC tv from our local OK furniture store and found out it has a defect on the one side of the screen with in 5 days of the purchase. Due to me changing the plug from a 2 point to a normal 3 point due to the nature of my enertainment setup they refuse to help me at all and say my garuntee is nul and void in full! I meani just spent R9000 on a tv and due to a change of a plug by a qualified electrician they dont want anything to do with me????