If the outlet says it can't be handled, the outlet staff doesn't know what to do. You can go directly to a bigger outlet. If the branch staff still refuses to handle it, you can ask them to ask their superiors, or call 8008295599 or 02 16 195599 customer service.
What is certain is that the money in the card will be taken out after the account is closed. Even if there is only a dime in it, you have the right to take it, and you must do it at the outlet.