I am encountering the same problem as well. I've already contacted ea support but they said they can't do anything
They're useless. The support team can't help me unlink the random steam account. I kept telling the EA customer service support rep. in the help chat that every time I tried to boot up BF3 from steam it would ask me for my EA account (✅) and to link my Steam acc. together (❌). Because my EA acc. was linked to a random steam acc. already, and because you can only be linked to one Steam acc. in a lifetime (stupid), It wouldn't be able to complete that process on my end. He kept saying that there was no steam account linked to my EA acc. but that wasn't true since I literally just tried linking it. Bro...the only solution is to just make a new account and continue. **bleep** dealing with EA they're useless.
