Unit Price Update after inventory deduction.

Hi Team, We are not able to perform the Unit price update for the Direct sales order after Inventory Deduction. We created new orchestration and change the fulfillment step in the orchestration. After that we can able to update the unit price for the new orders. But for the old orders which are waiting for Billing after inventory deduction we have issue. System is not allowing to update the Unit price. Is there any option we can use to update the lines in the old orders