I've switched from a smartphone to a feature phone. How do I unregister from my previous 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.