Change Healthcare is a juggernaut in the health-care world, processing 15 billion claims totaling more than $1.5 trillion a year, the company says. It operates the largest electronic “clearinghouse” in the business, acting as a pipeline that connects healthcare-care providers with insurance companies who pay for their services and determine what patients owe. In Florida, hundreds of millions of dollars in weekly billings have dried up and the damage could soon hit $1 billion.