Update iPhone to the latest iOS version
Check Settings for unknown profiles or device management
Review installed apps and delete anything unfamiliar
Check Safari for suspicious website data and extensions
Clear Safari history and website data
Review battery usage for unusual app activity
Review cellular data usage for unknown apps
Check calendar subscriptions for spam entries
Check email accounts and forwarding rules for unauthorized changes
Restart the iPhone
Remove suspicious VPNs, certificates, or configuration profiles
Change Apple ID password
Enable two-factor authentication
Run a security check on linked accounts and devices
Back up important data
Erase all content and settings if problems persist
Restore only trusted data after reset