Knowledge of product really bad

I bought a sinotec 65" smart netflix 4k tv from game stores, just to find out after hooking it up and putting my ps4 to it i cant set it to 4k, there is no option, i called the customer line the guy there didnt even sound like he new what i was talking about, all i need to know is how do i set my tv to 4k when i am playing ps4 or xbox one, its annoying how those selling the tv dont even know how to use it.