Select a conversation to start replying.
Country code first. Spaces, dashes and + are fine — they're stripped.
If this number hasn't replied to you in the last 24 hours, WhatsApp will reject plain text. You'll be told if that happens and can switch to a template.
Templates are the only thing WhatsApp accepts outside the 24-hour window.
Agents work the inbox. Admins do that too, and manage these accounts. Disabling keeps someone's history but blocks sign-in.
Share this with them over a private channel — they can't change it themselves yet.
Sign-ins, account changes and messages sent or deleted. Message text is never recorded here — only that a message was sent, and to whom.