Checkers house and home sucks

I bought a 70" TV from them and took an extended warantee. It was a JVC 4K. It keeps on freezing when watching Youtube or any videos. I also told them the same happens when sharing videos from my Pc.my colors was also out They told me to take it to Western Cape TV. They replaced the motherboard and told me the Tv was not designed to play and share from my computer. They also said they don't support any media players on-the TV.. so how must you watch videos on an 4K tv? I even tried a 4K movie from a USB drive. It still freezes. Hyperama staff have no technical knowledge and just listen to an uneducated supplier.