Hi Angie, 

Welcome to the Box Community!

Please be advised that you may only update the phone number in your 2FA via a web browser on a computer.

I've listed the steps below on how to update your 2FA in your Box:

1. Login to Box.com via a browser


2. Click on your account icon in the top-right corner of the page, and select Account Settings.
   


3. Under the Account tab, scroll to the 2-Step Verification section.


4. Click Remove next to the authentication method you want to remove, and then click Remove in the confirmation dialog box.


5. Then click "Setup" and choose your preferred 2FA method and then proceed.


6. Do not forget to click Save changes to save the changes you made

More details can be found in this article: https://support.box.com/hc/en-us/articles/360043697154-Multi-Factor-Authentication-Set-Up-for-Your-Account 

Best,