code: public function voidTransportRequest($request)
      {
          if (!($request instanceof FBAInboundServiceMWS_Model_VoidTransportInputRequest)) {
              $request = new FBAInboundServiceMWS_Model_VoidTransportInputRequest($request);
          }
          $parameters = $request->toQueryParameterArray();
          $parameters['Action'] = 'VoidTransportRequest';
          $httpResponse = $this->_invoke($parameters);
  
          $response = FBAInboundServiceMWS_Model_VoidTransportRequestResponse::fromXML($httpResponse['ResponseBody']);
          $response->setResponseHeaderMetadata($httpResponse['ResponseHeaderMetadata']);
          return $response;
      }
docs: Void Transport Request
  Voids a previously-confirmed transport request. It only succeeds for requests
  made by the VoidDeadline provided in the PartneredEstimate component of the
  response of the GetTransportContent operation for a shipment. Currently this
  deadline is 24 hours after confirming a transport request for a partnered small parcel
  request and 1 hour after confirming a transport request for a partnered LTL/TL
  request, though this is subject to change at any time without notice.
  
  @param mixed $request array of parameters for FBAInboundServiceMWS_Model_VoidTransportRequest request or FBAInboundServiceMWS_Model_VoidTransportRequest object itself
  @see FBAInboundServiceMWS_Model_VoidTransportInputRequest
  @return FBAInboundServiceMWS_Model_VoidTransportRequestResponse
  
  @throws FBAInboundServiceMWS_Exception