Unacceptable Response

Was advised to purchase a certain model DSTV decoder for my Extraview at Tafelberg Furnitures, Northgate and assured that that was all I would need. After purchasing the decoder for R499, the Installer tried for a few hours to get it to work, but no joy. Installer said that I would need a Smart switch for R660 to get the decoder to work. Tafelberg Tokai tried to help me as I really wanted Xtraview, and said I would need the smart switch. So I instructed the Installer on the next visit to go ahead with the smart switch. After installation the decoder would not work so he put in another new one. Everything worked fine after that. Upon returning to Tafelberg Furnitures, Tokai with the faulty decoder the next day, the store manager told me that they were having a lot of problems with this decoder but could not give me a refund! He said that I would have to go to Multichoice, N1 City to sort out the problem. So much for after sales service! It stinks. What am I supposed to do with a faulty decoder?