Removing Billing Documents from Rebate

Hello experts,

A user mistakenly settled a rebate agreement that is invalid (which means it should have no volumes inside). She has missed running VBOF to remove the volumes and went on to settle it. Now the rebate is in status C, and even if i try to return it to B, it won't have VBOF remove the billing documents as it has already been "settled".

Can you let me know if there's a way to remove them even if it's already "settled"?

Thanks!