Systems and methods are disclosed for providing a usage monitoring telephony service. A service-providing network, which has the capability of monitoring attributes, including duration, for calls that traverse it, provides usage-monitoring services for calls directed to a telephony device on a native transport network. The native transport network is a network that naturally carries a subscriber's calls but does not have the capabilities required to provide usage monitoring. The system uses a virtual number to map a service in the service-provider network with a device in the native transport network. The usage monitoring services capture usage-monitoring data for multiple telephone numbers in multiple native transport networks.