Step 1 : Speak ,
Speak to them kindly and make them to understand what you want to say about.
Step 2 : Warn ,
Warn them as speaking is not satisfied , warn them as everyone watch that so its safe to you.
Step 3 : Action ,
If you want to teach them a lesson complaint to your higher athorities about this and be united and if you need a break from them let you break them off....