The present invention relates to providing services for circuit-switched calls from an Internet Protocol (IP) based packet network. In essence, a call originating from or intended for a subscriber that is served by a telephony switch, such as an end office or mobile switching center, in a circuit-switched network is intercepted and routed by the telephony switch to a service node via a subscriber emulator. The subscriber emulator acts as a liaison between the telephony switch of the circuit-switched network and the service node of the packet network. Preferably, the subscriber emulator presents itself to the service node as a user agent, which acts on behalf of a subscriber that is served the telephony switch. The service node provides any requisite processing of the call to implement services for the call.