EA account linked to a Steam account that is not mine, can't unlink it?

Hello,

At the beginning of this year, my EA account was compromised.I subsequently recovered the account, changed my password and added two-factor authentication. I didn't immediately notice that my EA account had been linked to a Steam account that wasn't mine.

Today, when I tried to link my Steam account, I received a warning that another Steam account was already linked to my EA account. So I unlinked it from the "linked accounts management" page, and now I would like to link my Steam account to my EA account, but I keep getting the same warning that my EA account is still linked to the previous Steam account.

I can clearly see from the "account management page" that I have successfully unlinked the accounts. What else can I do? Do I need to wait a few hours before requesting a link to my Steam account? Does the process of unlinking Steam and EA accounts take hours, if not days?

I tried to open a case on ‘help.ea.com’, but I am only offered help pages that do not help with my problem. If I try to use the ‘Chat with an advisor’ option, I am told that ‘this is not a topic that advisors can resolve’ and I am never given access to any support chat. Furthermore, I cannot see my case saved anywhere.