1. The Defendant’s use of the mileage 11,250 C and the credit card amount from May 1, 2015 to April 30, 2017 to the Plaintiff.

1. Basic facts

A. Around April 2012, the Plaintiff entered into a credit card membership agreement with the Defendant’s telegraph Co., Ltd. (hereinafter “instant contract”) (hereinafter “the instant card”) (hereinafter “instant contract”) around April 2012, the Plaintiff entered into a G card membership agreement (hereinafter “the instant card”) with the Defendant’s general credit card holders (hereinafter “instant contract”) (hereinafter “the instant card”).

The term of validity of the instant card issued by the Plaintiff was until April 30, 2017. The annual fee was KRW 100,000,000. However, at the time of the instant contract, the Defendant agreed to provide additional services, including the provision of mileage at the rate of 2,500 won per 1,500 won, in addition to the services arising from the original function of the credit card.

B. Around February 1, 2013, the Defendant changed the percentage of mileage accumulation through the Internet homepage, notice, etc., announced that the percentage of mileage accumulation provided to the instant card members is reduced to 1.8 C mileage per 1,500 won per 1,500 won. Accordingly, the Defendant provided the Plaintiff with mileage accumulation rate from September 1, 2013 to April 30, 2015.

C. Of the Defendant’s standard contractual terms and conditions that were applied at the time of the instant contract (amended by December 13, 2010), the provisions related to additional services (hereinafter “instant standard contractual terms and conditions”) are as follows.

Article 14 ( Points and Other Services) (3) Additional services, such as points and discount benefits, provided on credit cards, shall be maintained without reduction or abolition for at least one year after the new issuance of credit cards, and when any additional services are changed, the change shall be made on the grounds, details of change, etc.