How to stop automatic updates of apps in iPhone?

If by ‘Automatic Updates’ you are referring to option found in Settings > General > Software Update, than that is not the setting that controls app updates, but iOS software updates, so the iPhone’s operating system.

Settings to control app updates are under Settings > App Store.

How to update apps manually on your Apple device

https://support.apple.com/en-gb/HT202180

Hello IsrThisNameTaken,

Thank you for reaching out to Apple Support Communities, and we'll be happy to help in any way we can. We understand you're having issues with apps updating automatically even though the option is turned off in Settings. To start, which exact version of iOS are you updated to under Settings > General > About? Did a particular app update or are all apps updating?

Cheers!