terrible service

I have posted before. I bought a 55 inch sinotec uhd tv. It doesn't play any 4k format. I download from youtube and play it and it says file not supported. Tried about 5 different formats none play via usb. Then I was told to call their technical number. I called. I get put through to various people. Some tell me to call and speak to Ian. Ian is never available. How can no one in the company know what format works??????? On the displays at store they play a video via usb displaying its 4k capabilities. Why is it so hard to see what format the file is? Also the TV said high dynamic range which is not the case. When I plug in the ps4 pro it tells me my tv doesn't support HDR. Is this false advertising?