I just finished calling a company that had this feature. So basically during the call, my call was disconnected. Once I phoned back, their PBX was able to detect that I just disconnected and was calling back right away. And it was going to do one of two options: 1) connect me back to the agent in which I was just speaking to or 2) if the previous agent is busy, it would put me back into queue, but at the top (first) so I can get assistance faster. I would love to see something like this with 3CX.