Cell phone use helps catch a Four State thief. Joplin Police say a man was seen trying to rob the Walgreens store on Main Street in Joplin, yesterday. The man was holding a kitchen knife and demanding money from the cashier. Police say customers inside the store immediately dialed 911 from their cell phones. They talked with dispatchers until the police were able to get there. Cell phones also were used by passengers on board the planes, which crashed into the World Trade Center, the Pentagon and in Pennslyvania. Those conversations could help the FBI in their investigation.