A new feature just got added to Packrooster Shipping Posti Smartship API. You can now book a pickup to your shipment from the carrier by setting a pickup time before the fulfillment.
You can set a default pickup time in shipping carrier settings, which will be the default pickup time that is sent to the carrier when creating a shipment.
Remember there must be at least a two hour window in the pickup time and the Instructions field is a required field!