Poor quality Tyres

I had 2x Continental Sport Contact 5 tyres fitted at Best Drive Krugersdorp on 3/12/2016. We have driven 14720 km on them and they are complete worn. Surely this cannot be ? I visited the the Best Drive fitment centre in Krugersdorp again today, they stated that there is nothing they can do, it has to be inspected by the manufacturer, Continental. They wanted me to pay for another set of tyres, after 15,000km. Absolutely not, but they were prepared for me to drive off again, so where does quality and safety come in ?Effectively they are making their problem mine by suggesting that I should be in contact with the manufacturer