When a user messages through WhatsApp they are not automatically associated with the existing user profile in Support that has the same email or phone number. Why are the users not correctly identified?
The first time a user messages through WhatsApp Zendesk will create a new user, even if their email or phone number is already associated with an existing user.
The newly created user profile in Support can be merged into the desired end-user profile. When the end-user messages in through WhatsApp in the future, it will be identified as the correct end-user upon ticket creation.
For more information about merging users, see the article: Merging a user's duplicate account.