(a) The obligor shall have twenty (20) days from the date of receipt of the national medical support notice within which to request a hearing. If the obligor does not request a hearing within twenty (20) days, the opportunity for a hearing may be deemed waived. (b) The request for hearing shall be made in writing to the court or tribunal having appropriate jurisdiction, with notice provided to the department, and shall state the basis upon which the hearing is requested. (c) The obligor may contest the withholding based on mistake of fact, according to the provisions of subsection (a) of this section. Notwithstanding any contest by the obligor under this subsection, the employer shall initiate withholding until the employer receives notice from the department that withholding is no longer required. Any funds that are found to be inappropriately withheld shall be refunded to the obligor, if no arrearages exist, in accordance with rules and regulations of the department.