To change a Business Unit on the Case Card, head over to the Details-view, under the Ownership and Acquisition section.
Click the 'Pencil'-icon to edit the Business Unit.
The following dialog will appear, enter the name of the Business Unit you want.
Select the Business Unit you want from the drop-down dialog, and you are done.
1. Ensure that you are either a Case Manager, a Client Manager, a User with 'Assistant'-role, or a User with 'Administrator'-rights set up to be able to make changes.