Stranger notifications

Those are spam/scam attempts.

If you are using iOS 13 or earlier: Settings>Passwords&Accounts>Accounts... delete the rougue calendar you (even accidentally) subscribed to

If you're using iOS 14 or later: Settings>Calendar>Accounts... delete the rougue calendar you (even accidentally) subscribed to

Regards

Giulio

🇮🇹

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. 

https://support.apple.com/en-us/HT211076

🇨🇦

My pleasure