The customer center number is 1666-0146, open weekdays 09:00~21:00 and weekends and public holidays 10:00~19:00. You can also email noc@telecentro.co.kr. Top-ups themselves run 24 hours a day regardless of office hours; only refund requests are tied to weekdays 09:00~21:00. The service is operated by QQTrade Co., Ltd. (business registration number 899-87-00639, Room 910, Ace Techno Tower 10, 196 Gasan Digital 1-ro, Geumcheon-gu, Seoul).
