A feature that lets users create and share event invitations directly within GroupMe chat groups.
For personal Microsoft accounts, Microsoft now says you can no longer add a phone number as a new security method. This method is being phased out. See official document here.
Are you hoping to update the contact method to receive the 2FA verification?
If so, you go to https://account.live.com > Security > Manage how I sign in. And you will need to use email, the authentication app, or passkey.