Virus attack on my iphone

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See: Delete spam calendars and events on iPhone - Apple Support.

Jack

Thankfully this isn't a true virus. Through a malicious email or website you got a calendar added to your phone.

https://service.mcafee.com/?page=shell&shell=article-view&articleId=TS103137&locale=en-US

This article shows how to remove the calendars. I would also recommend clearing all history and website data and updating your passwords as well after you do this.