How to prevent unwanted calendar spam?
How to prevent spam calendar events?
iPhone 11, iOS 14
Question marked as
To remove it, see below. To avoid it, do not accept offers from websites to send Notifications or other such freebies.
If running iOS 13 or earlier versions, check: Settings - Passwords & Accounts - Accounts - Any rogue entries here? If so, delete the rogue account.
If running iOS 14, check: Settings - Calendar - Accounts - Any rogue entries here? If so, delete the rogue account.
The Apple support article is below.