Sync your plans with your mobile calendar, so you can see your schedule even outside of Services.
Tap Calendar Link from the sidebar.
If you haven't enabled Services to access your calendar, confirm that you want to give Services permission to access your calendar.
If the calendar has access, when you tap Calendar Link, you'll get a confirmation and be able to access the calendar immediately by selecting View Events.
All calendars your device subscribes to will be shown. Select the calendar name to manage calendar settings.
Unsubscribe from the Calendar Feed
Open Settings > Passwords & Accounts, and tap Subscribed Calendars.
Select the calendar you'd like to remove, and then tap Delete Account.