Join Date: May 2012
Location: Munich, Algarve, Sussex or S.F Bay Area
Programs: Mucci, BA Gold, A3*Gold, LH SEN, HH Gold, Marriott Plat, IHG Plat Amb
Posts: 5,605
I had this issue with all my reservations after the recent BAEC IT changes. No idea why changing household account processing should make any difference, but whatever.
Try going onto the Finnair website, entering your normal BA PNR to view/change booking and enter your details there. It will modify the same underlying booking in Amadeus.