FAQ.yml - Add an entry for SMS Phone Authentication billing showing Microsoft Entra External ID

Author: msmimart

articles/active-directory-b2c/faq.yml

@@ -163,6 +163,18 @@ sections:
           * **Audit reports** include both admin activity and application activity.
           * **Usage reports** include the number of users, number of logins, and volume of MFA.
 
+      - question: |
+          Why does my Azure AD B2C bill show phone charges named "Microsoft Entra External ID?"
+        answer: |
+          Following the new [billing model](https://azure.microsoft.com/en-us/pricing/details/active-directory-b2c/) for Azure AD External Identities SMS Phone Authentication, you may notice a new name on your bill. Previously, Phone MFA was billed as "Azure Active Directory B2C - Basic 1 Multi-Factor Authentication." Now you’ll see the following names based on your [country or region pricing tier](https://aka.ms/B2CSMSCountries):
+          
+          * Microsoft Entra External ID - Phone Authentication Low Cost 1 Transaction
+          * Microsoft Entra External ID - Phone Authentication Mid Low Cost 1 Transaction
+          * Microsoft Entra External ID - Phone Authentication Mid High Cost 1 Transaction
+          * Microsoft Entra External ID - Phone Authentication High Cost 1 Transaction
+          
+          Although the new bill mentions Microsoft Entra External ID, **you’re still billed for Azure AD B2C based on your core MAU count**.
+          
       - question: |
           Can end users use a time-based one-time password (TOTP) with an authenticator app to authenticate to my Azure AD B2C app?
         answer: |