If you attempt to assign a WebRTC phone to a user who already has a WebRTC phone assigned to them, you will see the error message:

This person is already assigned  to a WebRTC phone.

appear below the Person box. You can avoid this scenario by using the WebRTC Person feature. When you add this feature to the Phone Management page, you get a searchable list that you can use to search for individual names to see if they already have a WebRTC phone assigned to them.

To enable and use the WebRTC Person feature on the Phone Management page:

1. Click Admin.
2. Under Telephony, click Phone Management.
3. Select the Phones tab.
4. On the top right of the column headers, click Select columns . 
5. In the Data to Display panel, click the WebRTC Person check box
6. Click Save and the WebRTC Person column appears on the Phones page.
7. To find a person, type a name in the Type to filter this page box and press [Enter].