Final invoice indicator is set automatically in MIRO for services

hello all

in our ECC6 system, the checkbox "final invoice " is acceptable automatically successful MIRO for services besides erstwhile the PO is simply a FO (framework order).

this is annoying arsenic successful FO, we invoice passim the full twelvemonth connected the aforesaid FO but the archetypal MIRO, sets already the last invoice indicator automatically!

with non-service materials, this does not happen. 

I tried to alteration the layout but it is not possible, since the checkbox is filled lone aft entering the FO number. Any thought connected however I tin alteration this?