To provide a communication system in which a user can revise the specifications of its own communication terminal even after purchase of it as well as on purchase of it and which selects a contract charge depending on the specifications.

A mobile phone terminal 100 as the communication terminal has a management memory 106 that stores specification information deciding the specifications. The user transmits specification revision information to revise the present specifications to a server 300 and updates the contents of the management memory 16 on the basis of the specification revision information in response to a reply from the server 300. Thus, the specifications of the mobile phone 100 are revised.