621—8.6 (20) Filing of a complaint. A complaint that any employee organization has engaged in or is engaging in any practice which constitutes a violation of Iowa Code section 20.25 may be filed in writing with the board by any affected person. Upon receipt of a complaint, the board shall serve a copy upon the employee organization by certified mail, return receipt requested. The board shall conduct a preliminary investigation of the alleged violation. In conducting the investigation, the board may require the production of evidence, including affidavits and documents. If investigation shows the complaint has no basis in fact, the complaint shall be dismissed and the parties notified. If the investigation shows reasonable cause to believe a violation has occurred, the board shall notify the parties. If the parties are unable to agree on an informal settlement after notification of reasonable cause, the board shall schedule the complaint for hearing.