An IP services switch that supports packetized voice traffic in the form of voice packets from a plurality of enterprises having a plurality of endpoints some of which can use the same IP addresses. The IP services switch includes a plurality of NAT tables, each of which corresponds to a separate enterprise network for providing header and payload IP addresses which are unique to the services switch for the voice packets corresponding to each separate enterprise endpoint. A method of NAT in an intermediate service provider network for header and payload IP addresses in VoIP voice traffic packets is also provided.