Step-up authentication force MFA either on Phone message or Email

We have enabled Phone message, Email as MFA factors. While requesting any sensitive scopes, I have a check in action to force user to complete MFA with any of the factors.


I have a special case like

  1. Complete step-up authentication with EMAIL while changing phone number
  2. Complete step-up authentication with Phone message while changing email

How can I force user to select only given factor to completing step-up authentication?