The Director of Communications shall develop a system of equitable billings and charges for communications services provided in any consolidated or joint-use system of communications. Such system of charges shall reflect, as nearly as may be practical, the actual share of costs incurred on behalf of or for services to each department, agency, or political subdivision provided communications services. Using agencies shall pay for such services out of appropriated or available funds. Beginning July 1, 2011, all payments shall be credited to the Communications Revolving Fund. Beginning July 1, 2011, all collections for payment of telephone expenses shall be credited to the Communications Revolving Fund.