Many Verizon Wireless customers are being billed for unexplained data overuse. In September, The Plain Dealer wrote about a few people who questioned exorbitant charges. Those stories quickly led to 4,000 Verizon customers from around the country contacting the paper with similar concerns. The reporters have stayed on the story, trying to determine what is wrong. All the while, Verizon says there is no widespread problem with its billing software -- while often erasing the charges that customers complain about.