I had a similarly frustrating issue happen with PayPal, only they were refusing to let me log in with my YubiKey, insisting on SMS. But their phone system couldn't send a message to me by SMS. It errored before it even tried, because I could have gotten a code on that phone if they had actually sent it.

If I've agreed to use and keep track of a very small physical device to access my account, don't be going letting any ol' person who can access my phone number in there!