You guys really screwed the pooch with this one!. We cannot add things into the Billing Statements section of the the document center. It needs to be editable
Is the document signed by chance? When a document is signed it is "locked," cannot be edited, and cannot be deleted. After signing a document, you may add additional attachments, but you cannot edit the original document.
If that is not the case we encourage you to contact support at 833-471-2273 for further understanding and troubleshooting.