Dstv installers in STELLENBOSCH

Hi one of my Dstv decoders had no signal, my wife got them on the internet, they came and look, saying they have to replace the thing by the dish (new) and a cable, they give me a prices of R 1375 then I said I don't have so much money, they came down with the price R 375. They start it wasn't 10 mins they are done, then I climb on the roof to make sure and saw that's a old thing they put in, they even showed me the box where it was in. When I confront them they wanted to argue with me, try to convinced me that it was part of the deal, they agree that hey were wrong. I told them to remove the thing they put in and put mine back just as they got it, they still wanted to argue with me but I said no take off and go. The fact that they wanted me to believe that it's new, if I didn't look on the roof my self I would've pay them all that money for a old thing. I don't know how many people they did this to. I really want people to be warn of this people, I think they are congolese. This is their no. ***