Violation of Consumer Rights

The store refused to take back a faulty decoder that keeps on freezing and long to switch on and I'm within my 6 months warranty and I'm being told that they only do 3months and by law any faulty goods I may have can be returned even without a slip, now the manager tells me that theirs nothing he can do and that I must just go to multi choice and they said I should return the goods were I bought it, the disrespectful manner they have towards customers is shameful now I just bought a new decoder and I want my money back this is a clear violation of my consumer rights.