Microsoft 365 features that help users manage their subscriptions, account settings, and billing information.
Please note that this forum is not Microsoft support, this is a user-to-user support forum. Therefore, I cannot directly escalate this for you.
If the tenant is a managed tenant, you will need to open a Microsoft 365 support ticket so Microsoft can review the domain ownership situation and determine whether a domain release process is available.
You mentioned you tried to open a support ticket via Azure Portal, have you tried to open ticket via Admin Center ? If not, please try it.
You can also contact support by phone, please visit the following page and reach out to phone number via: Customer service phone numbers - Microsoft Support
From what I know, you will need to get past the initial AI system to reach the live support team. You can refer to the guide below for tips on how to get through more easily: