K. Hovnanian review: Roofing 1

I found there is a leak on my roofing. The water leaked from the roofing to the ceiling of my garage. The dry wall of the ceiling was all ripped off. I called and contacted K. Hovnanian and the supervisor, Steve came with his roofing man, Steve. After Steve climbed and he inspected the roof he told me the reason it leaks is because I have lots of pine straws on top of the roof. I called couple roofing company and they came by inspected the roof. They all told me the builder, K. Hovnanian improper install the valley flashing.
My house is only 4 years old and the roofing is still under warranty. I believe it is K. Hovnanian's responsibility to fix my roof. If anyone out there experience same treatment from this irresponsible company please let me know.