I believe I have the same issue. I am playing on Playstation for the first time in 8 years, so when I tried to login with an EA account I was told I already had it linked to an existing PSN account ("Account A") . I *was* able to successfully unlink the old account ("Account A") and the EA rep confirmed it shows as unlinked on their end (photo attached). HOWEVER, every time I have tried to sign in with my new PSN Account ("Account B") I receive the attached message that the EA account is already linked to Account A. This is true for trying to log in to my EA account on both Google Chrome AND PS5 so it is not an issue with my PS5 downloading info (I have already restored licenses and hard reset the console).
I've contacted EA support multiple times and they say it's a "technical issue" and my complaint is simply not true. Either 1) it is taking EA servers DAYS to process account information updates (which us unacceptable for a global company) or 2) the linking system is simply broken and EA is deliberately lying to its customers. I've seen similar complains and just want to say I am actively not playing this game because of how shoddy the support system is.