Here's how to delete your Ringio contact from the Ringio application.  You may want to read these articles on how to add and share contacts, and knowing whether a contact belongs to you.

Recall that contacts belong to you if you added them manually into Ringio, or if you were the first person to edit the information of a contact that calls your group phone number. 

You will only be able to delete, share and unshare contacts that belong to you. 

You are looking at a shared contact if you see Shared by ... above the contact name when you click on that contact.  For this example, Sam Aparicio shared the contact 37 Signals.  A person who calls into your Ringio group/main line will be initially shared by the Ringio administrator until that contact's information has been edited and saved, with the contact now belonging to the first updater.

Step 1.  Sign into your Ringio application.

Click on your contact that you wish to delete.  You will see a delete button at the bottom right corner of the contact pane.  Click delete.

Ringio will confirm that you want to delete this contact.  Click Delete again to delete the contact, or Cancel to keep this contact.