I have this notification on calendar

It’s a Calendar phishing spam that added an account to your device. Do not click on any links or call any numbers in these entries.

Go to Settings > Passwords & Accounts and delete any accounts that you have not added, created or subscribed to yourself.

Please see: How to unsubscribe from calendars on your iPhone - Apple Support

See the post from Axel F. in this thread—>Spam in my calendar - Apple Community