Block a Device from being used as 2FA?

Is there any way for us to block the phone number/device from being registered as a device within the DUO admin portal?

Hello and welcome to the Duo community!

Currently, Duo does not have a feature that allows you to block specific devices or phone numbers from being enrolled as 2FA devices. However, 2FA devices can be deleted in the admin panel 2FA Devices section after they are enrolled. You can also restrict which types of devices or factors users can enroll on a global policy level.

Let me know if I can help further!

Thank you for letting me know!