Fortnite account bought and password changed nevertheless access?

I bought a Fortnite account a week ago and of course changed the password immediately after that, but whenever there's a round of gambling they have different skins, different levels and new friendship issues. How does he still access this account? And how do I manage that he has no more?

Well still logged in

Buy Fortnite Accounts is a) against the terms and conditions and b) just stupid.