Azure Admin Login

We have a client who has lost their access information to get into their Azure global admin. This is a non-profit institution that moved the ownership of their Azure account to another entity years ago now can't get in to the global admin for their entire Azure setup.

Microsoft requires the global admin login to create a support ticket and in this case, how are they supposed to open up a case when they can't login. The customer is furious and now disputing the CC charges so we open an Azure support ticket 10 days ago for ourselves and since it's not a Critical issue, have gotten no response.

This is untenable situation and there is no way to contact some one from MS without the login, how does this get resolved??