Help ylevelsoft.fun hack is placing events on my iphone calendar

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. 

Settings > Calendars > Accounts and remove any unrecognized ones. And don't agree to them in the future.