At the terminal the carrier releases the box only to whoever holds control on the platform. If that is a bank that refused and went quiet, the box sits and demurrage runs until someone talks the carrier into releasing against an indemnity. Dispose is an odd word for the record that opens the gate.
As far as I can tell, control stays with the bank until it moves it. Whether it may simply walk away is for the platform's rulebook and the bank's lawyers.
Karim is right that the box sits. The cost of it sitting is mine.
Credits are a small part of my season, but thirty days is not a window an exporter has. Last refusal we took, the grapes were already discharged and on the plug. I called the buyer that morning, had the waiver the next day, and never spoke to the bank at all.
Renata, the return line is worth writing. It does not press the button on the platform, though, and the quiet bank is the one that will not press it.
