Abstract: A voice call communication switching system in which a first network and a second network are connected to each other and which includes a user equipment that establishes communication using the networks and an application server that controls communication exchanged. The application server includes a message control unit that receives a message to be sent from the user equipment when a situation is changed from one where the user equipment communicates with another user equipment using resources of the first network to another where the user equipment communicates with the another user equipment using resources of the second network and a session end requesting unit that sends a resource release instruction to disconnect the communication between the first network and the user equipment to the user equipment. The user equipment includes a resource releasing unit that sends a message indicating release of the resources to a node.