Lost access to Microsoft Authenticator and had an old phone number registered

I've lost access to Microsoft Authenticator and had stored an old phone number. When I try to log in, I can't get a code or use any account recovery option available.

When trying to contact Microsoft Support by phone, I get the automated system that sends me again to aka.ms and then hangs up. When contacting Microsoft Support by Chat, two of the chats were disconnected, but the third one sent me here.

Does anyone have a solution to this problem?