I think someone trying to hack my phone

 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. 

Remove spam from Calendar on your iPhone

antonios16 wrote:

Still receiving suspicious notes in my calendar

Yes, you will until you follow the instructions noted above.

Also note, it is not a virus, not a hack. It is simply spam that you allowed on your device by accepting an offer to “send notifications”.

Your iPhone can’t be hacked. Why do you think someone is trying to?