[teh]

If you're sure there's no coverage where you are, you could just power down the phone and power it back up when you again reach civilization. I usually do this when working in the basement office at one particular university. The place is built like a bunker and I can't get any voice, data, gps, wifi or anything else down there, so if I leave the phone on it just gets hot and runs down the battery in a couple of hours trying desperately to reach a connection that it just can't reach. So I shut it off until I leave the building, as I won't have missed anything; I know I won't have been able to receive a call, so why burn up the battery? The only trick for me is to remember to power back up at the end of the day, as sometimes I get all the way home before I remember.