If I have misplaced my phone or have cancelled my wireless contract, how do I unregister from KakaoTalk?
Go to http://www.kakao.com/talk/ko/contact > Categories and select Unregister. You can unregister through Customer Service or independently through SMS verification.
If you are still unable to unregister, please contact the Customer Service with one of the following documents:
SKT users: User Agreement
KT users: User Registration Form
LG U+ users: User Confirmation Form
The date of cancellation/misplacement and your signature must be included in the document.