How to upload attachment to the manually created Blanket Purchase Agreements (BPA)

Summary:

Hi Team,

We would like to upload attachments ('TEXT' category) to the existing Blanket Purchase Agreements (BPA) which are created manually and in Incomplete (or) Open Status.

"ErpObjectAttachmentService" is only working for Converted BPAs i.e., whose document_creation_method is PODI/PO_WEB_SERVICE. But, not working for the BPAs created manually.

Is there any REST API or SOAP Webservices or any other option to upload the attachments to the manually created BPAs?

Content (please ensure you mask any confidential information):

Version (include the version you are using, if applicable):

25A, 25B

Code Snippet (add any code snippets that support your topic, if applicable):