No common carrier, except as otherwise provided, shall charge, demand, collect, or receive a greater or less or different compensation for the transportation of persons or property or for any service in connection therewith than the rates, fares, and charges applicable to such transportation as specified in its schedules filed and in effect at the time; nor shall any such carrier refund or remit in any manner or by any device any portion of the rates, fares, or charges so specified except upon order of the courts or of the department as may be now or hereafter by law provided, nor extend to any shipper or person any privilege or facility in the transportation of passengers or property except such as are specified in such schedules.