SPOILERS FOR BOTH SHOW AND COMIC BOOK
Originally Posted by washingtonmark
They did not say Carol was dead, and in my opinion that's who is on the phone because she is trapped in another room and needs help. Also I think Michonne is going to be one of the lasting important characters to Rick and co. She has great instincts and zombie killing skills she is also very smart.
In the preview, you hear Rick (or Daryl) say, "That's Carol's knife," so I think she's alive. Also, those who have read the comic know who is on the phone...