Close the pop-up tab or window
Force quit the browser app
Clear Safari history and website data
Turn on Safari pop-up blocker
Turn on fraudulent website warning
Block cookies from unknown sites
Disable JavaScript if needed
Remove suspicious calendar subscriptions
Delete unknown or suspicious apps
Check for and remove unknown profiles
Update iPhone to the latest iOS
Restart the iPhone
Use an ad blocker content blocker
Avoid tapping suspicious links or ads
Reset network settings if ads persist
Restore iPhone from a clean backup if necessary