Who’s Calling Rick in the Prison

Is Rick hallucinating the phone call?

So the official answer is that yes, Rick Grimes did in fact hallucinate the phone call in this episode of the show, the voices he was hearing were Shane, Laurie, Amy, Jacqui, and the guy that was digging, telling him that she is in a safe place, and others that had died at earlier points in the show.

Who is the woman Rick sees in the prison?

Lori is that sign. In the prison, in S3E9 “The Suicide King” Lori came to Rick as death. She was mysterious and away; dark and fearsome. Rick could be heard saying, “Get out of here, leave, get out!” This was actually what Lori was trying to say to Rick.