You should still be able to sign into the Azure portal with the account previously tied to the subscription; all that's needed is a work account or MSA. After signing in, you should be able to create an Azure Billing support request by following these steps: ...
- Sign into the Azure portal.
- Search for "Help + support" in the search bar.
- Select "Help + support" from the search results.
- Select "New support request".
- Select "Billing" as the issue type.
- Fill out the required information and submit the request.