In general, ancillaries that are voluntarily cancelled are non-refundable.
If, however, the ancillary is part of a ticket that has been cancelled by the airline, you should notify Gordian of the cancellation of the ticket using the inform cancelled endpoint. Gordian will at that point attempt to get a refund for the base cost of the ancillary from the airline. When Gordian is finished checking the refund, it will send you a refund check completed callback. If Gordian was able to receive a refund from the airline for the base cost of the ancillary, that base cost will appear as a refund on the next invoice you receive from Gordian.