Dear Miladi
Then only the way is ..Invoice correction request is better option
Or You do Cancel process --VF11--VL09--VL02N--VA02 and change the price and again Do same new process
OR Make it in copy control -- Price type -B And cancel the invoice and change the price it will affect in to billing
OR If Accounting document is not generated to FI Easily you can change Value in condition tab in Invoice
Let me know