I am sorry about the delayed response to your inquiry!
Do you use Twillio as a phone provider by any chance when authenticating users? I can see that in the provided code you set the phone number if the connection used by the user is sms.
The 20003 error code is sometimes associated with Twillion as mentioned in this knowledge article. The article contains a link regarding troubleshooting that error code.
Kind Regards,
Nik