If your issue cannot be resolved through Local Level Support, contact the Travel Assistance Center (TAC):
Defense Travel Modernization (DTM) prototype tech support, call 1-844-308-6880
Citi Customer Service: 1-800-200-7056 (collect 757-852-9076)
Citi Customer Service For APCs: 1-866-670-6462 (collect 757-853-2467)