general problems of the 1996 Toyota T100

I purchased four new tires 08-02-05 from hogan and sons in virginia, 9580 main st fairfax, virginia (703) 323-1044. Product goodyear, tires dunlop, product code 263-012-493-0. The first tire went completely flat with no signs of cause in Jan 06, the tire was replaced under road hazard warranty. I expressed my concern to the company where I purchased the tires and also had it replaced that the tires may be defective. I was told it was not defective. In April 06 another of the dunlop tires from the original purchase went completely flat. I returned the tire to a goodyear and again expressed concerns that the original set of tires may have been defective. I was told they were not defective and paid for a new tire, of the same brand and product code dunlop. I purchased a new tire at hogan and sons 4/21/06 to replace the spare also a dunlop with same product code. On 07-19-06 another of the dunlop tires, the newer replaced tires went completely flat with no signs of damage from an external cause. I telephoned hogan and sons who also stated they were affiliated with goodyear, that now a third tire had gone completely flat and I was concerned that there is some defect in these tires. At this time I am filing a complaint that the entire set of tires be replaced with another brand of equal price tires. The tires going suddenly flat have placed both me and those driving around me in danger on the road.