appwrite/docs/references/account/create-phone-session.md

Sends the user an SMS with a secret key for creating a session. If the provided user ID has not be registered, a new user will be created. Use the returned user ID and secret and submit a request to the PUT /account/sessions/phone endpoint to complete the login process. The secret sent to the user's phone is valid for 15 minutes.

A user is limited to 10 active sessions at a time by default. Learn more about session limits.