Locked out of Azure by MFA on a personal Microsoft account – only admin, need tenant recovery and subscription cancellation

My Azure subscription was created with a personal Microsoft account. The directory (tenant) has only me as administrator. Microsoft Authenticator no longer holds the registration for that directory (the entry was lost with an earlier phone), and no other verification method is registered. Sign-in to portal.azure.com therefore stops at "Enter code", and the security-info page itself requires MFA before a new method can be added, so self-service recovery is impossible.

The subscription belonged to a company that has since been closed. No services have been used for about a year, but a fixed amount is still charged to my card every month.

I need to (1) regain access, or have the subscription cancelled on my behalf, (2) stop the charges, and (3) request a refund for the unused period.

I cannot open a support request in the Azure portal because I cannot sign in to that directory, and a different personal Microsoft account has no directory of its own (the support blade returns AADSTS16000 in the consumer tenant). Could a Microsoft moderator please route this to the Data Protection / tenant recovery team? I can provide the tenant ID, billing profile and invoice numbers in a private message.