Check for suspicious apps you didn’t install: Settings → General → iPhone Storage → review installed apps
Delete suspicious or unfamiliar apps: press and hold the app icon → Remove App → Delete App
Review app permissions: Settings → Privacy & Security (and Location Services) → disable anything you don’t recognize
Check for unexpected profiles/MDM: Settings → General → VPN & Device Management → remove unknown profiles
Verify VPN settings: Settings → VPN → turn off any unknown VPN
Check for suspicious browser notifications: Settings → Notifications → Safari (and other browsers) → disable unwanted alerts
Review Safari website data/popups: Settings → Safari → Clear History and Website Data
Scan downloads and files you opened: remove any suspicious files from Files app (and delete related documents)
Update iOS: Settings → General → Software Update → install the latest update
Update apps: App Store → profile icon → Update All
Restart the iPhone: press and hold the side button and volume button (or follow your model steps) → power off → power on
If you suspect compromise, back up and restore: connect to a computer → Finder/iTunes → restore iPhone → set up as new or from a trusted backup
Contact Apple Support if you can’t identify the issue: Settings → Support (or use Apple Support online)