In a mobile communication network equipped with a wireless communication interface with a mobile communication terminal, when a need arises for disabling calling and card functions of a mobile communication terminal with a plurality of card information stored, there is provided a credit transaction system for permitting the process of disabling the calling and card functions of the mobile communication terminal, comprising a mobile station 100, a mobile telephone network 20, a mobile packet communication network 30, a CAT terminal 40a, 40b, . . . , the CAFIS network 50, a credit company's server 60A, 60B, and the Internet 70. Credit disablement flags are set in a control station 33, and the mobile station 100 receives a disabling signal from the control station 33 through a base station 31. The mobile station 100 subsequently deletes credit contract information stored in itself.