Dstv Multichoice Not Abiding With Consumer Rights

In less than 3 months after purchase and installation of Dstv decoder that comes with free installation the product is defective already and Dstv doesn't want to take responsibility for these costs as this job was done by an installer chosen by them and was directly paid by them for the services rendered. The installer didn't do a 100% job as now the units notifies of a faulty installation in less than 3 months. When I raise the issue with Dstv Multichoice they demand that I must take responsibility for the costs for the repairs which I find to be quite unfair as this be wasn't caused by my negligence. The Consumer Protection Act clearly states that within six months the consumer has the right to ask for a refund, repairs or replacement for any defective goods or services.