I can’t unlink a steam account that doesn’t belong to me

Yesterday I found out that my Apex Legends had been sold on a website. The user was able to play on it through steam. Fortunately, I still have access to this account, but I just can’t play when the other user of my account is on. Also, me and the other user seem to be able to share some of the legends purchased (not with real money hopefully). I’ve tried unlinking this account and apparently there is a 6 month wait before I can fully remove it. Is there a way I can bypass this? I do not own this steam account. 

Thanks