I also have an account with OP (albeit in a different regional cooperative bank). My interest rate adjustment date is this June, for which I requested a change in the reference rate from 12-month Euribor to 3-month Euribor. In the same context, I asked for a margin review, which they changed from 0.40 to 0.38 (I didn’t feel like pushing for any more). I have the same 200 € processing fee as well.