((a)) ** .—** A motor carrier or broker providing transportation subject to jurisdiction under chapter 135, including a motor carrier or broker operating within the United States while providing transportation between places in a foreign country or between a place in one foreign country and a place in another foreign country, shall designate an agent in each State in which it operates by name and post office address on whom process issued by a court with subject matter jurisdiction may be served in an action brought against that carrier or broker. The designation shall be in writing and filed with the Department of Transportation and each State in which the carrier operates may require that an additional designation be filed with it. If a designation under this subsection is not made, service may be made on any agent of the carrier or broker within that State.
((b)) ** .—** A designation under this section may be changed at any time in the same manner as originally made.