When you get a new smartphone with the same phone number, you will need to reactivate the device from the Duo Control Panel in order to use it for 2-Step.
Go to mycalnet.berkeley.edu and click Login in the upper right corner.
Log in with your CalNet credentials
When prompted to complete the 2-step select “Other options" and then "Manage devices"
At this point you will have to complete a 2-step in order to manage your devices. You can use an existing device, a security key, or a bypass code provided by the help desk.
Under your old device select "I have a new phone". Follow the steps provided by Duo in order to connect your Duo account to your new device.
Note: If you have set up a secondary device, you may use that to authenticate. If you don’t have backup passcodes or a secondary device, please contact calnet2-stephelp@berkeley.edu to get help.