While You Wait for the Truck
Shut the main water valve before anything else. If you cannot find it or it will not turn, the curb stop near the street can shut the supply, though it may need a special key. Next head to the panel, but only if you can get there on dry footing.
Water on the floor plus energized outlets is the hazard that hurts people on these calls. If water is touching outlets, cords or a power strip, stay out of that room and tell the dispatcher. Get papers, medications and valuables up and off the floor.
Dispatcher tip: Renting and cannot reach your landlord? Close the valve, photograph everything, and send a timestamped text and email so it is clear you moved fast.