the worst place I have ever been!

the worst place I have ever been!
before the sale he was super nice
I don't really know computers
I bought their graphics card and they make me believe that my power supply was wrong with me, who didn't know too much and trusted them
I take it I arrive dear me and my computer is not doing so well then I phone at another place I explain to them and tell myself that my power supply would have worked then I turn on my pc and it is slower than before I call them there tell me we opened the box we can do nothing so they had the money and now he answers no more and he hangs up allex never in this place there.
and the OWNER hangs up on me!