1. Open Office.com on your computer and sign in
  2. Click the purple Calendar icon which will redirect you to Outlook.com and sign in
  3. Select the menu icon in the top left corner (white dots)
  4. Select Calendar  
  5. On the left hand side, find the menu titled Your Calendars
  6. Locate the ECAL calendar subscription.
  7. Right click the name (Most likely the publisher name)
  8. Select Delete