Unlinking a device will delete all the backups you made on that device. If you do not have a local copy of your files, make sure that you download them first.
  1. Tap the menu button.

  2. Select My Files.

  3. Select Devices

  4. Tap the the option icon on the device you want to unlink.

  5. Press Unlink.

  6. Confirm that you want to unlink and delete all files uploaded from that device.