iPhone with 'Remote Management' after iTunes update

Hi, I bought an iPhone from the hand, I wanted to update it, otherwise it gave an error, I decided to update via iTunes after a successful attempt, the phone started, but the place of the usual login to iCloud, I got the inscription (remote management)

I googled it, it seemed that the phone belongs to some company and they all have some kind of password

I don't know what to do with it because the seller has evaporated

[Re-Titled by Moderator]

Original Title: Remote management