Power drops at the square of the distance if I'm correct.
For a point source, it does.
For a line source, it drops as the distance. E.g. the emissions from a power line.
For a plane source, it doesn't drop at all. E.g. a source that fills your field of vision.
I'd expect a cell phone antenna to approximate a point source when it's at a foot or so distance. An inch from your head, it probably drops less rapidly (in the nearby area).
Dave