change delivery date

-- HikaShop version -- : latetst business
-- Joomla version -- : 3.x
-- PHP version -- : 5.4.27
-- Browser(s) name and version -- : more ...
-- Error-message(debug-mod must be tuned on) -- : no error

I want to change the delivery day (choose between 3 days) after a customer has placed an order. I want to do that as a superuser of the site. I cannot do this in the order because when I change it there the system does not save the change but uses the original day.

Please advise me how to change the delivery day!

Kind regards.

Hello,
Can you give me more information about how you customers select their delivery day ?
Thanks.

Good morning,

after our customers have made an account or are logged in they can choose (drop down) between 3 delivery days (when tey fill in there adress, name etc) ; thursday, friday or saturday. Then they place and pay the order.
Is this what you mean by more info?

Kind regards.