Hi
You can use the followng FM/BAPI to read the full detail of your message.
BAPI_MESSAGE_GETDETAIL.
You can try in SE37 and executing .... by passing the parameters.
In your case, Pass the following parameters:
ID = VF
Number = 069
Language = 'EN'
Format = 'EN'
It will return message text -
Document is incomplete so billing cannot be carried out
Regards,
Venkat