The contractor will provide an On-call Telephone Support technical operations support service to the customer. This service will be available 24 hours per day and can be reached through a contractor provided toll free telephone line. Calls received during normal workday office hours of 0800-1700 hrs Central Time, Monday through Friday, excluding holidays, will receive a response not later than four hours of receipt. Calls received during weekends, holidays, and periods outside normal workday office hours will be responded to not later than four hours after the start of the next normal workday. On-call Telephone Support services provided encompasses any problems associated with the day-to-day operation and customer assistance issues