In remote areas where cellphones don't work ham radio may still do the job. Hams maintain repeaters throughout the country on mountain tops and in other accessible locations. They can frequently be used when cell phones fail.
I will be CG hosting in the Sierras this summer in just such a location and will have a 2m ham transceiver along just in case the Park Service radio conks out.
Of course you need a valid ham license to legally access these. That's not difficult to obtain and is free or close to it. There will be a local amateur radio club in your area that can get you started.
Joe
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