The dispatch center is free to build and gives you an overview of all your stations, staff and vehicles and a central point to manage it all plus some comfort functions that are available with a Premium Account.
Additionally it expends the radius in which your stations can generate incidents, which is useful when POIs are set out of the range of your stations, since the best missions only spawn at POIs.
You can disable a dispatch centre if you don't want to have missions in a certain area. To disable the dispatch center click on the edit button in the dispatch center menu.
You can have one dispatch center for every 10 stations.