죄송합니다. 잘 못 알아들었습니다.
Use this when you didn't understand what someone said and need them to repeat or clarify.
죄송합니다. 다시 한번 말씀해 주시겠어요?
죄송합니다. 잘 못 알아들었습니다.
Use this when you didn't understand what someone said and need them to repeat or clarify.