Faulty accelerator

I bought a new Mazda 3 Neo Sport in 2008. I was very happy with my 2008 Mazda Neo Sport for the first couple of years, but there is a recurring problem that has not yet been resolved and the car is now out of warranty. In 2010/11 the accelerator got stuck on full throttle while driving, but the dealer was unable to find the fault. The problem occurred a few times since, including once when I had the cruise control on. It has happened both on the freeway and while driving around town. No fault codes have been logged by the vehicle computer system. The issue is frustrating and dangerous, and the only way to stop the vehicle from over revving is to pull up, brake hard and turn the ignition key off to stall the engine. Mazda dealerships don't seem interested in resolving the problem and I am desperate for technical information.