17.5.1 update by Apple without my permission

Turning off Automatic Updates after a failed update will only prevent automatic downloads for the next update, not the current one.

Here's why:

• iPhone remembers your update intent: Once you initiate an update, even if it gets interrupted, your iPhone recognizes your desire to install the latest iOS.
• Automatic Updates act as a convenience: This feature is designed to streamline the update process by automatically downloading new versions in the background. Disabling it simply prevents this automatic download.
• Manual update check still possible: You can still check for updates manually by going to "Settings" > "General" > "Software Update." This will allow you to resume the interrupted update or download a new one if available.

Please check if both Automatic Download and Automatic Install is enabled.

See the pic below which is self-explnatory

Just updated my old iPad with 17.5.1, set to off, in General settings. Only security downloads are allowed. The last upgrade was bad enough. I am finding my settings mean nothing anymore. Also, Siri gave me a suggestion when I was speaking to my sister. All settings but side button activation is off. I said, Siri. Your settings are set on no listening. Why are you listening and responding to me. It turned off.