A knowledge base article about My 2-Step account has devices listed that I no longer use. How do I remove them? provided by the UC Berkeley IT Service Hub - Knowledge Portal
To remove a 2-Step device from your account, follow these instructions:
Warning: Ensure you have at least one other active device or a set of backup passcodes before deleting a device to avoid being locked out of your account.
If you need more assistance, please contact calnet2-stephelp@berkeley.edu.
See also: KB0012361 - How to Add a New Device or Reactivate a Replacement Phone