It is possible to configure the system to automatically notify Customer or Account via e-mail available credit (current Balance plus Credit Limit) reaching certain threshold. That setting can be accessed via the "Additional Options" menu from the Accounts interface.
From the drop-down menu select "Auto-Recharge / Notifications" option.
Set your desired threshold amount into the Threshold field or set it to "Disabled" from the drop-down menu to deactivate automatic notifications.