They're here for the poor souls who get into fender-benders and need to call 911, only to find their cellphones are dead. They're here for the hapless tourists whose cell providers don't work in South Florida. And they're here for millions who can't afford a monthly land line or long-distance bill. But they won't be here for long. Pay phones -- the trusty, clunky, plastic-and-metal standbys favored by Clark Kent for his Superman transformations -- are going the way of the dinosaur.