OneDrive 2FA Recovery Assistance

I can still sign in with my usual OneDrive password, but the login stalls at the text-message step and the registered phone number is gone. I have already opened a ticket with Microsoft support, yet days later I am still waiting for a real answer, so I am turning to an expert here.

What I have: full access to the primary email address tied to the Microsoft account, proof of ownership of past billing for Office 365, and other details that confirm the account is mine. What I no longer have is the mobile number originally set up for two-factor authentication. I did not save backup codes.

I need somebody who knows Microsoft’s account-recovery workflow inside out—whether that involves filling out the advanced recovery form with the right level of detail, bypassing the old number through alternate verification, or escalating the request internally at Microsoft. A clear, step-by-step plan (and if necessary, a brief remote session) that ends with me back in my OneDrive is the only deliverable.

If you have successfully handled locked-out Microsoft 365 or Azure AD users before, please outline the approach you would take and an estimated timeline.