Iphone Hack related

Your phone has not been compromised, it's just a scam message designed to trick you into buying unnecessary software.

Here are the instructions on how to remove the bogus calendar

Delete spam calendars and events on iPhone - Apple Support

This is a user to user support forum.

it is not instant messaging or chat.

You post your question and wait for another user to respond.

The calendar entry in question is spam that you allowed a website to place in your calendar.

Remove it :

Delete spam calendars and events on iPhone - Apple Support