No changes were made errorr in change document (FB02)

Dear SAP Experts,

I have a problem of changing document in FB02. User wrongly created a document without cost assignment information. Thus, I want to make changes in it to reverse (because document is cost element). But I can't save the updated information & the message "No changes were made" shows.

The importing DATA_OUT is same as old information(different with DATA_IN) in the function 'G_VSR_MULTI_SUBSTITUTION_CALL' that is included in the "FI_SUBSTITUTION_DOC" function when debugging. I think that's the problem when updating documents but I don't know how to fix it.

Your reply would be great help!

Regards,

TRA