When a service providing server receives, from a mobile phone or the like owned by a user, a request to modify a parameter defining the performance of a control device provided in an automobile, the service providing server transmits a requested modification command to the control device. The control device modifies the parameter thereof in accordance with the modification command received from the service providing server. Further, the service providing server records a history of the modification command having been transmitted on a user-by-user basis, and settles an account of the user every predetermined period of time, by requesting the user to pay a fee for the modification. Thus, a service provider is able to charge the user for modifying various parameters defining performance of the control device.