I want to turn off the two-factor verification on my iPhone and iPad

2 Factor Authentication 

From the article below. 

Can I turn off two-factor authentication after I’ve turned it on?

If you already use two-factor authentication, you can no longer turn it off. Certain features in the latest versions of iOS and macOS require this extra level of security, which is designed to protect your information. If you recently updated your account, however, you can unenroll for a period of two weeks. Just open your enrollment confirmation email and click the link to return to your previous security settings. Keep in mind, this makes your account less secure and means that you can't use features that require a higher level of security.

Apple ID -Two-factor authentication.   *

RyanPinnick wrote:

It won’t let me turn off the two factor verification

Two-factor authentication for Apple ID - Apple Support