So in order to Play online i need to log in with the EA account that registered the Key to Play Online?
Re-read my post. You have to purchase the actual game. The key you purchased online is illegal
. It will NOT work to allow you to play online. Go to a store, go to Steam, whatever and purchase the actual game, not the key. You are playing an illegal copy right now and that is not tolerated here.
Once you have purchased a legal, legit copy of BC2, then you'll be able to play online. Until then, you will receive no further help here because pirating is not condoned at Tom's Hardware.