My device is hacked

Your device is not hacked. If you are seeing spam information in your calendar, it is because you inadvertently clicked on a spam subscription. See this for removal. Remove spam from Calendar on your iPhone - Apple Support

You got tricked into installing a rogue calendar; your phone does not have a virus.

If your phone has iOS 13 or earlier: Go to Settings/Passwords & Accounts, look under Subscribed Calendars, tap on the offending calendar and delete it.

If your phone has iOS 14: Go to Settings/Calendar/Accounts, look under Subscribed Calendars, tap on the offending calendar and delete it.

And in the future beware of "free" offers

Apple phone never hack bro but some software issue is all time so check software