I would do a series of games on a paid retreat. Everyone would have to play, not just management.
Game 1: Split into teams to build various buildings with certain specifications using wooden blocks. A counselor or trained professional would observe who is doing what communication-wise during that game and devise other learning opportunities.
Game 2: A hide and seek game with a twist. One set of teams is given paint mixing sticks. The other set of teams has balloons. They have to hide and avoid getting their balloons busted by the stick wielders. Anyone whose balloon is burst must take a stick and join the stick wielders. Anyone who goes to home base before time is called must give their balloon to another person who has a balloon. Time is called at least four times. They can't stay on or very close to home base. The team with the most balloons left at the end has to explain how they communicated with each other to get it done. Also evryone discusses how improved communications would have helped them win.
If it has to be incorporated into the work training, then i seriously would be in trouble coz i would not want it to be done in the process of serving customers. I would want it to be done a certain day, certain time, mandatory. It's a game too. :D
Game 1: Simplest one you've ever done as a child. The leader tells a secret to one person. That person passes it on, then the next, then the next, then the next. You get to see how it changes by the last person and discuss that.
Game 2: Split into teams and pick different things to say to each other (from a box or hat) and instead of responding, tell what you think that person means. Talk about how important interpretation, point of view, delivery, etc. can be in communication.
Game 3: Make everything they learned STICK and enforce the rules and policies. Make it clear the games were for YOU to see what they are like and for THEM to see what they are like and now they have to follow the policies and apply what they've learned.
I'd have some taglines that people use when they're getting things done during the workday when they work as a team, especially. Everyday each department discusses for a few moments what they are going to accomplish and then they wish each other the best, basically and then help each other do it!