incompetant mechanics and supervision

New Mazda BT50 lost power 10km outside Polokwane on my way to Pretoria. No warnings was given. I checked the water trap for dirt or water and found it to be clear. I took the vehicle back to Polokwane and send it to galactic auto to check. This vehicle is still under warrantee. First thing they do is to put it on the computer and tell me the diesel pump is broken due to water in the fuel. I told Hannes that I check the water trap when this happened and found it to be clear. I also told them that I drove Izuzu bakkies for 15years under the same conditions and never had the same problem, the filtration system is supposed to clear the diesel from impurities and water. I also have 2 other bakkies and plant on site using the same fuel, and they do not have the same problem. Suddenly he changes his story and say there are other impurities in the diesel and that he is not sure if it is the diesel. From experience a few years ago with a different vehicle they gave me a list of problems that the computer said is wrong, I looked at the list and told them the items on the list will not solve my problem. They them changed these items charge me for it but the car was still the same.