No response from hisense SA

I bought a Vida Tv 55" 2 - years ago and now apps keeps on dissappearing on the tv. I phoned hisense about it and gave a ticket no to follow it up. I was told the technician will contact me its over a month now no calls. I kept on phoning hisense and i get promises that someone will call me. The app in question is Prime video. I am paying prime video subscription but i cant watch it anymore. I was told to buy TVBox.