Error "Already enrolled" while selecting sms as MFA option on login in Auth0

I’m using lock widget for authentication, and custom MFA page. When a user is prompted for mfa, upon selecting sms option and entering a phone number, following error is thrown.

I’m using custom phone message hook to deliver sms, but due to the above error, the hook is not being triggered (hook is enabled and required mfa settings are set correctly too. it’s working fine with test-runs). I tried logging in with various mfa-enabled users & phone numbers but the error persists for all.

I also get “Pro MFA” plan exceeding warning.