What are the hours of operation for customer service? Emily Taylor February 11, 2017 03:54 Updated Follow Daily Hours of Operation for Diamondback Fitness Customer Service: Monday-Friday 9am-5pm (MST) Closed Saturday/Sunday. Closed National and State Holidays. Related articles Where is the nearest Diamondback Fitness retail location or dealer (USA)? How do I reach customer service? Comments 0 comments Article is closed for comments.