I had this issue a couple years ago trying to go back and play bad company 2.
I had changed my Steam account email so when trying to log on to EA with Steam it asked to verify the email address I had already closed years prior and wouldn't let me do anything so I eventually stumbled on a way to Unlink the account, from there this situation has only turned into hours of confusion. To me this is nonsense.
I've tried creating new EA accounts to link to my Steam and anything else you can think of and from what I can gather my Steam account (which has not been compromised, never been banned in any way, never was banned on EA ever) can never be linked to a EA account again?
I feel like this need a reported to like an EA engineer or something, there must be thousands of people with this issue by now. Top it off I've been trying to get through to EA support for DAYS and can't even get as much as a confirmation email that my support request was received.
That's a sign something is very, very broken. A company so worried about security it has thrown customers overboard. I will for no reason whatsoever buy games through EA, I game on Steam and only Steam. You want my money then this needs to work better in the future.