I want to turn off 2 factor verification on my i phone 12

See this article --> Two-factor authentication for Apple ID - https://support.apple.com/HT204915

"You can manage your trusted phone numbers, trusted devices, and other account information from your Apple ID account page." --> https://appleid.apple.com/

You can’t turn off 2 factor authentication. You will have to troubleshoot why you are not getting a code. And if it is working correctly you will hardly ever need the code; only when you log in to https://appleid.apple.com or https://icloud.com.