Ghost Call: 
(Opening Spiel) 3x
I am so sorry, but I cannot hear any response from the other line, I have to disconnect this call. If you have pending concern, please call us back at 1-800-864-8331. (Do callback after)
Make sure to advised your TLs, SMEs or any available Leads on duty if staffing permits a call back.

Callback Process: (All Disconnected Calls)
Hi! This is (your name) from United. I am making this callback because we got disconnected a while ago. This call is being monitored and recorded for security and quality assurance purposes. Am I speaking with (name of the customer)? State the resolution or continue with the interrupted process.