Whats the proper process for updating a user phone number in Starling?

Hey guys,

Just a quick question, but first the background:

The helpdesk wanted to preemptively setup one of our retail stores for 2FA, and asked if it would be possible to set the phone to her phone, do the setup with the desktop client, and then once its done, change the phone number?

I don't think this is possible because the phone number is authoritative and key for the 2FA process, but according to my wife, I can be wrong.

I know this is going to come up again, when a user gets a new phone, or goes from wanting to use their desk phone to the mobile phone. So what would be the approved process to change that, and whats the turn around time for that?