You can unlink your Appointy calendar from Integration section of your Admin console (Settings --> Integration --> Facebook --> Click to unlink your Facebook account. (It will only remove the linking).
To remove an app from your Facebook page :
1. Login to your Facebook account, click on **Settings** at the top of your Page.
2. Click **Apps** in the left column.
3. Go to the app you want to remove and click (x).
4. Click Remove.