(a) The department shall provide centralized telephone service for state agencies, each house of the legislature, and legislative agencies in the capitol complex. State agencies in the capitol complex shall use the service. Each house of the legislature and each legislative agency shall use the service at the discretion of the legislature. The department may provide the service to other state agencies that subscribe to it.
(b) Each using entity shall make monthly payments to the department when billed by the department.

(c) Each using entity may arrange for its own terminal telephone equipment, but the equipment must be compatible with the centralized telephone service. The department shall make terminal equipment available for using entities that choose to use that terminal equipment.
(d) Not later than October 1 of each year, each using entity shall, in a manner determined by the department, provide the department with an e-mail address for each person who uses the centralized telephone service.
(e) Not later than December 31 of each year, the department shall prepare and issue a revised centralized telephone service and e-mail directory.