They sold us a faulty fridge

My aunt bought a KIC fridge im their Tzaneen store. The fridge would work and other times not work. They sent a technician to come fix it and he told us that the fridge has a factory fault. The Technician by the name of Lawrence then went back to KIC and reported that the fridge had been tempered with. So they cancelled the warantee of the fridge. We have been trying to tell them what Lawrence told us and that the fridge has never been tempered with but they refuse to listen.