How to delete custom domains from Azure AD

I'm trying to register a custom domain in my Azure Active Directory, but, when I try to verify this domain, it says that my domain already been using by another Azure AD or Office 365.

We do not have Office 365 and there's only one AD in Azure.

I tryed to run the "Get-AzureAdDomainNameReference" in Azure Cli logged as a Global Admin user to discover the references pointing to my domain, but I receive this error:

Get-AzureADDomainNameReference: Error occurred while executing GetDomainNameReferences Code: Authorization_RequestDenied Message: Insufficient privileges to complete the operation. RequestId: 6d04656f-ece1-494e-a78d-e06eaaf6a692 DateTimeStamp: Sat, 23 May 2020 15:52:12 GMT HttpStatusCode: Forbidden HttpStatusDescription: Forbidden HttpResponseStatus: Completed

I want to delete all references to this domain, to register it in my Azure AD from scratch. How can I do this?