Unable to unlink account on a used Series S

I bought an Xbox Series S off of Facebook, but now i can't play Battlefield because the old account is linked. I have opened multiple cases, and i cant believe why it is so difficult to change an email address. I cant play a game I own, this is ridiculous. Has anyone had this problem and solved it? One of the suggestions was to create a new xbox account, i was blown away they suggested this compared to changing something as simple as an email address.