My friend can't hear me during a Video Call/Voice Call.
1) Go to your device settings and make sure that your microphone has been enabled for KakaoTalk.
2) Please make sure you have not set your microphone to Mute during a Video Call/Voice Call.
3) Your friend should also check to be sure that his/her device has the volume up.
도움말을 통해 문제를 해결하지 못하셨나요?