Radiator problems of the 2013 Volkswagen GTI

I drove 4 miles and notice my coolant light come on and decide to park my vehicle. The very next day I notice coolant was very low and had big leak. I jacked the car up and notice the leak was coming from engine and not the radiator. Having much experience working on cars. I dissemble the entire front to my engine and notice the water pump/thermostat housing profusely leaking. It was not a gasket job, but a warp and hairline fracture coming from under the thermostat housing. I purchase a new water pump/thermostat housing for $317 at the dealer although it was under warranty. It was very meticulous work and did not want the dealer (teddy Volkswagen) to do a slopping job. They already did a sloppy job on previous radiator inspection. I demand a refund and the service lady ( niki) stated they have to do the work. I said forget it and storm out of the dealer. I am 100% sure this will occur again, it is a bad design to use plastic in a high heat area in the belly of a turbo engine that warps and cracks the plastic housing -- metal design withstand the heat much better!!!!! bad engineering!! why plastic ????? this needs investigation and recall ASAP on Volkswagen behalf!.