A method and system for network-based control over voice calling from a client telephony device. A client telephony device receives a user-request to place a voice call from the client telephony device and responsively sends to a controller, via a packet-data connection, a request for authorization to place the voice call. The client telephony device then receives from the controller, via the packet-data connection, a response to the request. And the client telephony device then sends to a network entity (e.g., a switch) a call origination request message seeking to initiate the voice call, only if the response from the controller indicates that the client telephony device is authorized to place the voice call. Further, the controller can also monitor a account balance for the client telephony device and direct the device to disconnect the call when the balance is exhausted.