Brake Electric Antilock problems of the 2002 Mazda B3000

On several occasions, my Mazda truck b300 v6 model has locked up on its brakes. The vehicle comes equipped with an abs (four-wheen anti-lock system) which prevents it from locking up during driving conditions. However, on four varied situations in location, weather conditions and mileage apart 20,000, 30,000-35,000, 40,000 (considering three of them was before I hit 50k and then after getting my 60k service matienance)61k, my front end tires locked up while merging onto a highway; turning leftu nderneath an underpass; proceedin forward on a major road in houston, TX; and while just making a normal turn, not a sharp turn, but turning into a neighborhood, austin, TX. I in all occassions have had my foot firmly applied to the brakes and stilli lost control of the steering, with both my hands on the wheel, and had to turn the truck off after managing not to hit the car directly to my left on at least three reoccurrences. All under rainy or wet conditions where the road was level, normal, congested, or going downward on a smooth slope in elevation. I mentioned it to the dealership twice and was told that, that lost of traction was due to elevation of the truck and pressing the gas while I turned left. On the past three occassions I did not have my foot on the gas turning, ever while turning. I like my truck, but I could've had caused some major car wrecks due to some malfunctioning.