How do i contact one call concepts? One Call Concepts - Corporate Office 7223 Parkway Drive Suite 210 Hanover, MD 21076 Telephone Number: 410.712.0082 Fax Number: 410.712.0838What is oneone call? One Call is a growing healthcare network management company and the nation’s leading provider of specialized solutions to the workers’ compensation industry. Toggle navigation +1 (866) 697-2680 Why choose one call? We are moving people through their care journeys better than ever before, providing exceptional, predictive, and responsive care coordination. As a leader in the workers’ compensation industry and ancillary services for Medicare and Medicaid, One Call has an unwavering commitment to getting people the care they need when they need it.