If the plane was over the ocean when it went to 45,000 feet (IMO as part of a plan to decompress the cabin and kill the passengers), the plane would have been out of cell phone range. I think this was a sick but well-conceived theft of the plane by either the pilot, co-pilot or a crew member who had access to the cockpit.
See my last post. There is no such thing as being out of cellphone range.