A special-purpose Service Control Point includes a customized application that provides Fixed Mobile Convergence services and interoperates with a Voice Over Internet Protocol (VoIP) network to achieve a single-number fixed mobile convergence overlay network. By determining if a dual-mode cellular/WiFi handset is reachable via a WiFi network, the Service Control Point may redirect incoming and outgoing calls off of the cellular network and onto the WiFi network, thereby reducing cost and providing greater coverage.