For China visa application, you have to use the official list of travel agency, however, the service fee of travel agencies should be not more than 20, 000 won. The two travel agencies (Xanadu, Kangsan)has infringed the rules on service fees
You can write e-mail (mfa.gov.cn|consulate_korea) or fax (02-755-0469) to lodge a complaint (complaints by phone or face to face are not accepted). You should write down clearly your real name, gender, date of birth, nationality, passport number, phone number as well as the application date, the name of the travel agency and the details regarding the infringement. The Consular Section of the Chinese Embassy will fully investigate the case and deal seriously with the relevant travel agency.