In a communication control system 1, in an acquisition step of acquiring routing information before a line is set, a first mobile communication switching device 100 generates an acquisition request signal of routing information, which includes calling/called number specifying information and call information, and transmits the acquisition request signal to a subscriber information management device 200. The call information includes calling number information specifying a calling-side mobile communication terminal 600 and call type information representing a type of a call from the calling-side mobile communication terminal 600. The subscriber information management device 200 specifies a called-side second mobile communication switching device 300 based on the acquisition request signal and transmits an issuance request signal of a routing number to the second mobile communication switching device 300. The second mobile communication switching device 300 transmits the call information to a called-side mobile communication terminal 700 when a calling signal for acquiring the routing number is transmitted to the mobile communication terminal 700.