Any officer or employe who has authorized the making of deductions from salary, wages or other compensation as aforesaid, may revoke the authority to make such deductions by delivering a written revocation to the officer or officers involved at least fifteen days before such revocation is to become effective; and thereupon, the officer or officers involved shall cease to make any such deduction from the salary, wages or other compensation of any such officer or employe.
40 P.S. § 542