I can't get rid of a spam calendar item

I got a spam calendar invite the other day and didn't realize it. As i was accepting other invites I accidently accepted this one. I realized right after I accepted it that it was spam so I went to the calendar and declined the event but it doesn't go away. There is no option to delete it only decline it but no matter how many times I decline it still shows up. I have the phone set to not show declined items and all my other declined items don't show, just this one. How do I get rid of it?