Information relating to a transmittable data amount differs depending on a service provided by the application server 30. Thus, the application server 30 determines a transmittable data amount for each communication terminal 50. Note that the application server 30 is disposed outside the mobile network. In other words, the application server 30 may be managed by a carrier differing from a carrier managing the mobile network. Thus, from the perspective of security and the like, the control device 10 does not directly receive information relating to a transmittable data amount from the application server 30, but receives information relating to a transmittable data amount from the application server 30 via the service control device 20. As described above, the service control device 20 can determine whether information from the application server 30 is reliable, by having a function of authenticating the application server 30.