Once a shipment has been picked up by the carrier, any change you wish to make to the shipment must be done directly with that carrier. There are no options within ShipStation to modify the shipment once it is on its way.
If you need to stop, redirect, or intercept a shipment, you will need to contact your carrier directly. Fees may apply for any changes made to a shipment that is already in transit to its destination.
For parcels shipped using ShipStation Carrier Services, you can also contact ShipStation support to contact the carrier on your behalf.