How to turn two-step verification off

If your truly still using the legacy 2 step verification system -> Two-step verification for Apple ID - Apple Support (I.e. not the current 2 factor authentication system -> Two-factor authentication for Apple ID - Apple Support) then follow the directions from that first link.

”How do I turn off two-step verification?

Make sure that you're still signed in to iCloud on each of your devices. You might be asked for your Apple ID password.

1. Sign in to your Apple ID account page.
2. In the Security section, Click Edit.
3. Click Turn Off two-step verification. Click again to confirm.
4. Create new security questions and verify your date of birth.

You'll get an email confirming that two-step verification for your Apple ID is off.”

But if using account features that now require 2 factor authentication (iCloud Keychain, messages in iCloud, Apple Pay, home kit, etc) you may only be allowed to change 2 step verification to 2 factor authentication and not completely remove 2 factor logins for your AppleID.

IF it has been more than 14 days since it has been activate it can't be turned off, if not defer to the documentation when you first signed up for it.