Unassign purchase organization from a company code

Greetings,

We are currently working on the latest SAP S/4HANA Cloud version and we had a Purchase Organization (PO) that wasn't assigned to any Company code and we assigned it to one unintentionally. We'd like to undo this by unassigning it from the company code and leaving it again as a cross-company PO. This is supposed to be possible, and the way to achieve it is described on a help sap documentation. It states the following:

- On the left-hand side pane from the organizational structure choose the purchasing organization for which you wish to reassign the company code assignment.

- On the top right-hand side of the detail screen for the purchasing organization, select Edit Company Code Assignment.

- In the dialog box Edit Company Code Assignment, select None.

- Choose OK.

Link to the cited sap documentation: https://help.sap.com/docs/SAP_S4HANA_CLOUD/c6383e7f1b504995a26a9a28797de152/4da665df2454482895db67d021fc7534.html?locale=en-US

We've tried to follow the previous instructions on the Manage your solution App but we are unable to find the "None" option, it just doesn't appear among the ones you can select, all we can do is change the assigned Company code for a different one.

On the other hand, I managed to find a PO that was not assigned to any Company Code and, when pressing the previously cited Edit Company Code Assignment dialog box, you can actually see that it has the option "None" selected. This makes us think that the "None" option is only available as long as you don't assign the PO to any Company code, because once you've done it, you can't undo it.

Thank you very much for your help in advance.