The 7 pin plug has an adapter attached to it that will plug into the 4 pin adapter on the wiring harness installed by Kia. In addition, the 7-pin plug will have three wires that control an additional things like brakes etcetera on the trailer. Those three wires need to be plugged in to the specific source of power on the Kia. that's the general idea of how you would hook up a 7 pin plug. I'm not sure if the wiring confusion on the dealers behalf is because their vehicles are not normally used as towing vehicles or if the new technology that controls adaptive braking plays a part.