3. Why would he imagine a woman’s voice he doesn't know and on a clear phone line have a conversation with her and then tell him they will call back in 2 hours, then a call back in 2 hours with a man’s voice he doesn't know on a clear phone line and then have Laurie talk to him on a weird sounding crackly phone line?
The characters (the the actors who play them) that called were Amy, Jim and Lori. The Talking Dead confirms that. Sarah was actually calling Andrew from Canada for that seen since she had already left the show.