Any authorization to withhold from the salary, wages or annuity of an employee or annuitant shall terminate and such withholding shall cease upon the happening of any of the following events:
Upon termination of authorization to purchase United States Savings Bonds, any amount withheld from the salary or wages of an employee for such purpose and which has not been so used shall be immediately remitted by each Office to the person from whose salary or wages such amount was withheld.
5 ILCS 365/9