Follow these steps to un-claim an Avi-on device from your app account:
First, you must log into the user account that was used to claim the device.
Tap the "three vertical dots" icon then the "pencil" icon to access the device's details page.
Tap the menu in the upper right corner of the detail screen for that device.
Tap "remove", then verify that you would like to remove that device.
The device must be turned on and in range for the un-claiming process to be successful.