We highly recommend that for the age groups of 2022/2021 & 2020/2019, the coaches use their whistle to stop/freeze the players. That way, when the players are playing a game and hear the whistle, they will understand to stop.
Teach this by using games!
Players dribble a ball in a zone and freeze when they hear the whistle.
Variation... The players can stop the ball with different body parts (Foot, Knee, Sit, Tummy, Back, etc)
The players will dribble the ball from one end of the field to the other. When they hear the whistle, they should stop. Begin when they hear GO.
Before giving the players a task, you should say, "When I say go, ... (say the task) ..., GO!
This concept should help you make sure the players listen to your full instructions. It frequently happens, coaches are describing a drill/activity, and the players rush into the drill before the full instructions are given. It is normal, they are curious and excited. So use the "When I say go, ..., GO!
For example, "When I say go, I want you to dribble the ball to the red cone and then dribble around the blue cone, GO!"