Qaz

You have to contact the person who's account is on your phone and ask them to remove it using their account password.

There is no other way. If you bought it like that, return it for a refund.

If this follows the usual paths, either you were sold a brick and the seller has undoubtedly now disappeared, or you logged into and transferred your iPhone ownership to an Apple Account controlled by another. Or maybe you found a brick, and are trying to use it.

You got scammed. Pay the ransom, or recycle the brick. It’ll never be useful.