A. On April 2012, the Plaintiff entered into a credit card subscription agreement and issued a credit card (hereinafter “instant contract”) with the Defendant through the Defendant’s Internet credit card website, and entered into a credit card subscription agreement with the Defendant (hereinafter “instant card”) and received the instant card.

At the time of the instant contract, the credit card company was G. However, on September 1, 2014, G transferred all rights and duties regarding the credit card business portion to H corporation after dividing the company into H corporation. On December 1, 2014, H corporation merged the I corporation into “B corporation,” which is currently the Defendant’s trade name, and without distinguishing the company before and after the alteration and merger.

The card of this case is a credit card with C mileage (it may be converted to E or F mileage) accumulated in the ratio of two days per 1,500 won per additional service, and annual fee is KRW 100,000.

B. Around February 26, 2013, the Defendant changed the mileage accumulation rate: (a) announced that from September 1, 2013 to April 8, 2015, the rate of accumulation of the instant card was reduced to 1,500 won per 1,500 won; and (b) accordingly, the Defendant accumulated and provided mileage to the Plaintiff at the reduced rate from September 1, 2013 to April 30, 2015.

C. The part of the Defendant’s standard terms and conditions applicable at the time of the instant contract (amended by December 13, 2010), among the Defendant’s personal member terms and conditions (hereinafter “instant standard terms and conditions of additional services reduction”), concerning the reduction of additional services (hereinafter “instant standard terms and conditions of additional services”).

Article 14 ( Points and Other Services) (3) Additional services, such as points and discount benefits, provided at the time of the use of a credit card, shall be maintained without reduction or abolition for at least one year after the new issuance of the credit card.