...
Calls originating in the VoIP network will appear to users on the PSTN as originating from one of the assigned DID numbers.
...
You’re life is even easier: Automation
In addition to a visual interface, VoipNow also offers billing engine operations. With a regular IP PBX you most likely would have to export call records and then process them either manually or with another software product. This is not time effective and the reports may not be precise. VoipNow’s charging plans automate this operation for you and its call history based reporting is always exact.