Won't accept resposibillity

On 27 March my vehicle's engine seized as a direct result of Mechanico and its personel not knowing how to safely lock the cranck before working on, and set the timing of my Renault Scenic. My vehicle was handed to Mechanico because the accessory belt broke but they informed me that the crank pulley has broken upon which I instructed them to replace it. Instead they had it welt and refitted the unit, not informing me. After fitment they could not succeed in resetting the timing and after the vehicle being returned to them for three times to have it set, I still could feel the timing was out. Their GM, Angelo van Wyk, instructed me to continue driving with the vehicle and to just call them if I had any problems. As a result of the timing issue, the pistons hit the valves and as a result the damages on the vehicle amounted to well over R 25 000. I had the extent of the damages and cause thereof confirmed by a reputable company and technician. The owner, De vaal van der Merwe, insisted they will not take resposibillity because they did a favour to the company that sent my vehicle to them and insisted their warranty is not applicable as they did not charge them for the work done!