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.