When a first user intends a call with a second user via a packet switched communication service (e.g. VoIP), but the second user terminal or second user is currently unavailable to answer a call through the packet-switched service, then a call intent notification is sent to the second user terminal via an out-of-band communication channel, the call-intent notification notifying the second user about the intended call. Includes in the notification is a gateway PSTN number enabling the second user terminal to establish a hybrid PSTN call with the first user terminal via a connection between the second user terminal and a gateway over a PSTN network, and via a connection between the gateway and the first user terminal over the packet-switched network using the packet-switched communication service.