The Wilderness Reality
You're on your own. This is the number one message preserve visitors must know and apply to their visit to Aniakchak. There is no cell phone service and there are no amenities, services, or other infrastructure in the monument or preserve. When you depart you may not see another person until your return to civilization or your pilot comes to pick you up. Visitors must be self-reliant and able to execute self-extraction and communication, should an emergency situation arise.
Cell phones do not work in Aniakchak. Satellite phones provide far better coverage and it may be wise to consider renting a satellite phone before your trip to the park. You may also find that a satellite-based text messaging device will meet your needs.