1. An information service system that provides a telephone information service to a service user through a telephone connected to a public line, comprising: an interactive system that implements an interactive control apparatus for providing information or executing processing according to an interactive script in response to a request that has been made by the service user through voice or push button operation; an interactive log management apparatus that manages an interactive log related to the usage of the interactive system; and a call charge burden ratio calculation apparatus that calculates the ratio of the burden of call charges associated with the telephone information service between an information service provider and service user based on the interactive log managed by the interactive log management apparatus and call charges information associated with a use of the interactive system.