KakaoTalk is a personal message.
The message API provided by Kakao Developers has various restrictions according to the Korea Personal Information Protection Act.
Checklist to use the Messaging API and the Retrieving list of friends API
Therefore, informational messages and counseling messages(상담톡) should use channel messages provided by the Kakao business.
DevTalk provides information about Kakao developers, so we do not know the exception case of Kakao business.
Could you ask the customer center below if you can build BizMessage by yourself?