Poor and unfair service at Ok furniture store.

Hi my sister and husband bought a Hisense 58 inch smart tv today at Orange Farm Eyethu mall. But TV was not brand new it was a display. They bought it around 3 when they got home they played it like for 5 seconds showing a green line. Then after TV went off. They went back to OK store and was told there's nothing they can do it means they did something to television. Sales assistant that was assisting them was not available due to he has a personal problem. There for manager said he can't attend to them due the the person that sold item to them is not present and he did call someone but he's not sure if the situation will be solved. So I was asking Hellopeter to please intervene in this situation. Cause they sitting for almost 3 hours still in the store with no help. My sister saved up money to be able to buy this smart TV. And was also her last. It would truly not be fair for the TV not be changed by OK. Cause they truly did nothing to the TV. Please Hellopeter please intervene.