A monitoring device 132 provides a shared call stack to a monitored extension and one or more proxy extensions. For example, the monitored extension is a boss' extension in a business environment, and the proxy extension is an extension for a boss' secretary. The monitoring device 132 detects an incoming call for the monitored extension. The incoming call is redirected, by the monitoring device 132, to a shared extension that is associated with the monitored extension. The shared extension has a shared call stack. The shared call stack has a call stack position that is shared with a proxy extension. The incoming call is made available as a call option in the call stack position so that the monitored extension and the proxy extension can user the monitoring device to perform call functions on the incoming call. The monitoring device can also perform call functions on outgoing calls.