Internet Traffic Billing

Hi,

Is there a third party application that is use for billing clients base on their Internet usage?

Possibly using NPM historic internet utilization (total bytes transferred graph) or NTA reporting? I notice that when generating a report (Total Bytes Transferred by Interface - Last Month) it doesn't look right (see attached screenshot).

We are more after an application that can pickup real Internet traffic and disregard traffic internally (between VLANs).

We 2 physical interface on our Cisco 3800, WAN and LAN. Clients (different businesses) are separated using dot1q on the LAN creating sub-interfaces (screenshot)

Help.

Thanks