Open Settings
Tap General
Tap Software Update
Tap Automatic Updates
Turn off Download iOS Updates
Turn off Install iOS Updates
Open Settings
Tap App Store
Turn off App Updates
Open Settings
Tap your Apple ID name
Tap iCloud
Turn off iCloud Backup if you do not want automatic backups before updates
Keep the iPhone in Low Power Mode when needed to delay some background update activity
Avoid connecting to Wi-Fi and power at the same time if you want to reduce update prompts
Delete any downloaded update file from iPhone storage if one is already installed in storage
Open Settings
Tap General
Tap iPhone Storage
Find the iOS update file
Tap Delete Update