Microsoft 365 E5 Developer Program Phone Number Issue

Hi,

This is a known limitation with the Microsoft 365 Developer Program, and it can be confusing.

The error you’re seeing usually means that your phone number is already associated with an existing Developer Program account. Microsoft allows only one active developer subscription per user, and the phone number is used internally as a unique identifier.

Can you try below steps to see if you are able to sign in or recover your account?

Sign in instead of signing up Try logging in here using any Microsoft accounts you may have used previously:
https://developer.microsoft.com/microsoft-365/profile

Recover accounts linked to your phone number
Use the account recovery tool to check if your phone number is associated with any Microsoft account:
https://account.live.com/username/recover