CTM Springs - Their taps don't hold water.....

I have purchased close to R100k's worth of goods from this branch in this month as we are renovating. I purchased a Carlita Freestanding Mixer - this was displayed and when I asked they said its only because it is the last one. I should have known its too good to be true. Now that it is installed - properly by the way - it doesn't work correctly and it leaks. I went there yesterday and asked them about this - they then logged a service call for them to come out to our home and fix it. When they called I told them it was already assembled. They informed me that then it does not carry a guarantee and I should ask for a credit back and get another one. I was not informed of this when purchasing or even yesterday when I visited the branch. So where does this leave me? I can't return it and get another type as all the plumbing will also need to be changed? I want a new tap - the SAME one.