No modification of either the designated sales territory or any territorial agreement shall be effective (i) until written notice thereof shall have been given by the manufacturer or importer to the wholesaler; (ii) until written notice thereof, together with the affidavit of the manufacturer stating that the level of service within the designated territory will not be adversely affected by the change, shall have been filed with the board; and (iii) until the board shall have verified that the level of service within the designated territory will not be adversely affected by the change. Provided, however, board verification shall not be required where the board has suspended or revoked the license of the wholesaler, shall not be unreasonably withheld and shall be completed within a reasonable time not to exceed 30 days from the date of filing with the board. The notice shall be given after recognizing all rights of the wholesaler and duties of the manufacturer or importer. Nothing in this chapter shall impair or alter contractual rights, duties or obligations of manufacturer, importer or wholesaler, including but not limited to the termination thereof.