Hi @Joseph Rizco ,
To prevent the Calendar app from displaying automatically in the Teams client, we can unpin the Calendar app by right clicking it and choose "Unpin". See Unpin an app.
The pinned apps can also be controlled by configuring the app setup policy in the Teams admin center, see Manage app setup policies in Microsoft Teams.
But please be aware that users would still be able to find and use the Calendar app through a manually search, and as far as I know, this is currently unavoidable:
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