Have you checked on the website checkmytrip.com?

I don't know the validity of the information given through checkmytrip on airberlin, but I have flights coming up in May (award using Avios) where both my flights have my seats shown as "confirmed".

On a previous award trip, using AA miles, I actually called airberlin directly to pay for advanced seating (which worked out fine). How did you pay for the seats? Over the phone?

I believe the only way that I checked my preassigned seats (on an AA award) on airberlin was through checkmytrip. I can't remember definitively though.

Hope this helps. airberlin isn't the best for these ordeals. My previous trip actually listed me as a "Mrs.". Luckily I had no problems and no extra questions coming back into the US.