Immediately after you register an IoT SIM, its status shows as Ready, meaning it is ready to communicate. When it communicates in this state, the status changes to Active.
If you do not want it to communicate yet (for example, before deployment), deactivate it from the User Console or via the API. This sets the status to Inactive, and no data communication occurs.
(Even when Inactive, some devices may attempt a session, but no session is established and no charges are incurred.)