If you have lost checked baggage or taken the wrong bag off the belt, you need to contact the airline you are traveling with or the ground handling agent that handles baggage for your airline. Go to the airline webpage for further information.
Overview of handling services at your airport: Choose airport, click on the menu and select contact. Here you will find contact information for airlines and ground handling agents.
When you call the airport, all major airports have a dial option for missing luggage. You will then be transferred to a handling agent.