Locked out of root account (lost MFA + stolen phone) - support case stuck for hours with no callback

Update: My case has been resolved. Here's how it went, in case it helps someone else in the same situation:

1. I kept following up on the same support case thread, confirming my availability and an alternate phone number each time.
2. After a few call attempts that dropped or went to voicemail, AWS Support requested notarized identity verification: a completed and notarized "MFA Identity Verification Form and Affidavit" (downloadable from AWS's support documentation), plus a photocopy of my government ID (front and back).
3. I had the affidavit notarized locally (in my country, not the US - a local notary public was accepted).
4. I submitted the notarized affidavit and ID copies as attachments in a reply to the support email.
5. AWS reviewed the documentation, approved the MFA removal, and gave a mandatory 24-hour security waiting period before removing it.
6. After the MFA was removed, I was able to log in with my email and password, pay the outstanding balance that had suspended my account, and everything was restored.

Total process took several days, mostly due to notarization and back-and-forth on call attempts, but it does work. Hope this helps someone else going through the same thing.