A. On January 12, 201, the Plaintiff entered into a mobile communications service contract (hereinafter “instant contract”) with the Defendant, who is a telecommunications business operator, for the phone number B, and entered into a mobile network service contract (hereinafter “instant contract”). On September 16, 201, the Plaintiff, a mobile network fee system for the use of unlimited data, which is a mobile network fee system for the use of unlimited data, (i) the amount of basic fees reduced to KRW 1,000 and the name was changed to KRW 54,00; hereinafter “instant fare system”).

At the time of entering into the instant contract, the Plaintiff and the Defendant agreed to regard the terms and conditions of use (hereinafter “instant terms and conditions of use”) as the content of the instant contract (Article 2(1) of the instant terms and conditions of use), and the main contents of the instant terms and conditions are as follows.

Part I of the General Provisions of Chapter II (Application of the Terms and Conditions) ① This provision shall apply to the use of mobile telephones, and the provisions of the relevant Acts and subordinate statutes and the individual use contract (agreement, etc.) shall apply to matters not specified in this provision.

Part III. (Obligation of the Defendant) ① When entering into a mobile telephone service contract, the Defendant notifies the customer of the major contents of the contract and the use of the service, such as the charge system, additional service, customer complaint settlement body and telephone number, object of reduction of or exemption from the charge, criteria for suspension of use and ex officio termination, etc., which the customer must know, and if not notified, he did not claim the right thereof.

(15) Where important matters (charges, supplementary services, etc.) relating to the services provided by the defendant are modified at the customer’s option, the defendant shall be notified to the customer through Sms, E-Mail, etc., and shall post the details of the change on the website.

B. On January 13, 201, the day following the conclusion of the instant contract, the Plaintiff shared data capacity as a fee system for additional services of the Defendant’s “T data Shephering OPD”.