Thank you for your post!
I understand that you're having issues adding your Cell Phone as an Authentication method within your user's Azure AD Profile.
When it comes to adding other authentication contact information to your actual signed in user's Azure AD Profile, you'll have to use the Access Panel Profile, specifically the My Sign-Ins Security Info page.
Manage user authentication methods for Azure AD Multi-Factor Authentication
If you're trying to add Authentication Methods for other user's within your Azure AD tenant, the UI experience will allow you to add it via the Portal.
If you'd like the UI experience to be different, I'd recommend leveraging our User Voice forum and creating a feature request, so our engineering team can look into implementing this.
I hope this helps!
If you have any other questions, please let me know. Thank you for your time and patience throughout this issue.
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