Integrated Cellular Voice over Internet Protocol ("VoIP") systems ("ICV systems") are described that redirect or reroute wireless network voice and data traffic to roaming subscribers via VoIP networks. The ICV system monitors roaming links of a first communication system. The first communication system may include a home network and a visited network. The ICV system detects a mobile device registering with the visited network. The ICV system receives location information corresponding to a location of the mobile device and selects a routing number corresponding to the location. The ICV system uses the selected routing number to transfer calls received at the home network to the mobile device via a second communication system.