Microsoft 365 features that help users manage their subscriptions, account settings, and billing information.
Dear Nitin Mazumdar,
Good day!
Thank you for posting to Microsoft Community. We are happy to help you!
According to your description, This issue with phone number validation during Azure Subscription Sign up can be resolved by creating a support ticket and working with our billing team or Azure subscription team.
please be kindly to contact Microsoft Billing team directly and tell them that "Your phone number did not pass security checks".
They would be able to add your phone number into the whitelist.
To get in touch with Microsoft Billing team, please refer -Find Microsoft 365 for business support phone numbers by country or region - Microsoft 365 admin | Microsoft Learn.
Or Help + support - Microsoft Azure
Thanks for your precious time and your understanding would be highly appreciated.
Hope you all the best!
Sincerely,
Eben / Microsoft Community Moderator