It depends on the agent. The problem lies in the call centre system. Without elaborating on internal procedures and information, sometimes an agent can call back a Pax. Sometimes they cannot. As of late more agents do call back if the call is dropped (remeber the call back system that AC implemented a few months ago when wait time is too long? That brought in some changes at the call centres). But generally speaking it's still a rare-ish occurence and will be for the time being, but it's far from being a 1 time deal also.

Cheers

Edit: for clarification I'm talking about gen res, not sure about concierge.