At the end of each month, a summary of the usage data (data, SMS and voice minutes) is generated.
You can obtain the billing data for each completed month via the menu item "Billing". Switch to "Usages" in the left navigation bar and select a completed month next to the search form via "Filter":
You will now see the consumption per ICCID. By clicking on "Actions" and "Export" you can export the data for further use:
If you have maintained the field "Endconsumer ID" in the device overview under "End customer" (submenu on the page), you can see this field with in the export. If you calculate the consumption of sub-customers, you can use this to assign the SIM card to the customer.