Brakes Failed problems of the 2006 Chevrolet Silverado 1500

Purchased 2006 Chevrolet silverado 1/2 ton pickup truck new. At 2400 miles, I started experiencing a pulsating in the brakes that created a severe shimmy in the steering wheel when the brakes became warm. The dealer resurfaced the two front rotors. The problem continued. At 6500 miles, the dealer stated the drums were out of round and replaced them. At 13,000 miles, problem still persisted and dealer replaced front rotors. At 21,000 miles, the problem was still occurring and I inquired with a different dealer who test drove the truck and said they have had this problem with other vehicles, including the impala automobile and stated that there is no fix for the problem. In may of 2008, I placed a call directly to gm's customer service and received a return call from a gentleman who stated he was calling from argentina to respond to my complaint. All that accomplished was for him to arrange another appointment with the original dealership for another inspection. At 23,000 miles, the dealership suggested that when I am driving down a steep incline that gm advises I should use a lower gear to help reduce the vehicle speed and not create an overheated condition which they say was causing the vibration. The vibration occurs on level ground as well as coming down a hill and it is becoming increasingly more difficult to control the vehicle when this occurs and may lead to an accident if the brakes fail.