Block carrier billing or lower its limit

Blocks purchases charged to your phone bill (휴대폰 소액결제), or lowers their limit, so purchases cannot be charged to your phone bill without you.

How to do it

SK Telecom: block carrier billing or lower its limit online in T world, by calling 114, or at a store with your ID card.
SK Telecom: if you keep carrier billing on, set a payment password (휴대폰결제 비밀번호) through ARS 1509.
KT: in the My KT app (마이케이티) or on kt.com, open 마이 › 요금/서비스 › 요금조회 › 휴대폰결제 내역 and set the limit to 0 won or withdraw your consent to carrier billing. To add an ARS PIN check (ARS 안심인증) when you pay, call 114 (KT says this is free). To block it completely, use the 원천차단 button in the same menu or call 080-722-0100 (account holder only). KT's notice of 10 September 2025 says this block can never be lifted, except blocks set up because of the situation at the time, for which it said it would announce a way to lift them.
LG U+: block it in the U+one app (≡ › MY › 휴대폰 결제 › 결제 차단/해제), on the LG U+ website (MY › 가입 정보/사용량 › 휴대폰 결제), in the PASS app or by calling 114. Lifting the block needs identity verification. Budget carriers: ask your carrier's customer centre.
App store purchases (Google Play, App Store) are a separate setting, so check their payment methods as well.