(2) Administer oaths, summon and compel by order or subpoena the attendance of witnesses to testify in relation to any matter which, by the laws of this state relating to insurance, is the subject of inquiry and investigation, and require the production of any book, paper, or document pertaining to such matter. A subpoena, notice, or order under this section may be served by certified mail, return receipt requested. If the subpoena, notice, or order is returned because of inability to deliver, or if no return is received within thirty days of the date of mailing, the subpoena, notice, or order may be served by ordinary mail. If no return of ordinary mail is received within thirty days after the date of mailing, service shall be deemed to have been made. If the subpoena, notice, or order is returned because of inability to deliver, the superintendent may designate a person or persons to effect either personal or residence service upon the witness. Service of any subpoena, notice, or order and return may also be made in any manner authorized under the Rules of Civil Procedure. Such service shall be made by an employee of the department designated by the superintendent, a sheriff, a deputy sheriff, an attorney, or any person authorized by the Rules of Civil Procedure to serve process. In the case of disobedience of any notice, order, or subpoena served on a person or the refusal of a witness to testify to a matter regarding which the person may lawfully be interrogated, the court of common pleas of the county where venue is appropriate, on application by the superintendent, may compel obedience by attachment proceedings for contempt, as in the case of disobedience of the requirements of a subpoena issued from such court, or a refusal to testify therein. Witnesses shall receive the fees and mileage allowed by section 119.094 of the Revised Code. All such fees, upon the presentation of proper vouchers approved by the superintendent, shall be paid out of the appropriation for the contingent fund of the department of insurance. The fees and mileage of witnesses not summoned by the superintendent or the superintendent's designee shall not be paid by the state.