All parties to contested cases shall be afforded an opportunity for hearing after reasonable notice. The notice shall state the time, place, and issues involved as specifically as may be practicable. At the hearing all parties shall be afforded an opportunity to present evidence and argument in accordance with the rules of the commission; provided, that informal disposition may also be made of any case by stipulation, agreed settlement, consent order, or default; and provided further, that this section shall not be applicable to proceedings otherwise provided for by law.