First of all thank you very much for your help, you have been really helpfull for me!!
I would like to share how I solved my problem.
As I told you, all configuration was made but message that there is no entry in T028G still appeared.
I still can`t find the error but debugging I noticed that in table FEBP there wasn`t transaction key for my statement so I filled it there manually.
I know that problem persists (and I continue making tests) but the user was able to post the statement so now, it is not urgent.
Thank you very much for your help again.