Any party in interest who intends to avail himself of the opportunity to be heard, shall personally appear on the date set forth in the notice of hearing or on any adjourned date and shall be prepared to proceed. Any such party may be represented at the hearing by an attorney who is a member in good standing of the Bar of the State of New York or the Bar of the State of New Jersey. Any such attorney shall file a written notice of appearance on a form furnished by the commission. After an attorney has so appeared, all further notices, orders and other communications from the commission may be served upon such attorney and such service shall be deemed to be service upon the party in interest.