If you would like to specify a billing department to associate with your Royal Mail OBA billing departments you can do by going into your Royal Mail settings and clicking on the billing department drop down menu

From here you can select exactly which billing department you would like your OBA shipments to be related to.

If your billing department is not appearing in the list, please press Refresh Department List and this will pull through any of your billing departments

If you have any issues with this or any queries relating to this, please contact support