How to reverse "Post goods issue" for partial delivery?

Hi expert,

My business scenario as:

I have created a sale order (QTY:10), and create a delivery order for the sale order,and then I changed the delivery QTY in the delivery order and "post goods issue", and then create billing document for the delivery. At the same time,I have change the SO after change the delivery QTY. Now I have cancelled the billing doucment,but I can't reverse the "Post goods issue", Due to the "partial billing" status in the delivery order.

Can anybody help on this case?

Thanks,

Don