220 ILCS 5/13-505
Any proposed increase or decrease in rates or charges, or proposed change in any classification, written service offering, or tariff resulting in an increase or decrease in rates or charges, for a competitive telecommunications service shall be permitted upon the filing with the Commission or posting on the telecommunications carrier's website of the proposed rate, charge, classification, written service offering, or tariff pursuant to Section 13-501 of this Act. Notice of an increase shall be given, no later than the prior billing cycle, to all potentially affected customers by mail or equivalent means of notice, including electronic if the customer has elected electronic billing. Additional notice by publication in a newspaper of general circulation may also be given.
220 ILCS 5/13-505