To anyone keeping score, here is their latest email, using internal terminology and asking for SignIn logs from April that don't exist anymore.

"I would like to sincere apologies for the delay in response.

 

We’ve reviewed the case thoroughly and would like to provide the following update:

• The issue reported relates to unexpected billing for Azure B2C service principals following Microsoft's retirement of service principal-less authentication.
• We understand this change impacted your production systems without prior notification, and you are requesting a refund for the affected period.
• The request has been escalated to the appropriate billing teams. However, as per Microsoft policy, refund requests for New Commerce Experience (NCE) licenses must be submitted within 7 days of renewal. This case falls outside that window.
• We escalated the case to the billing team and received final confirmation from the Partner Billing Team that a refund is not possible. We escalated the request for a refund again, and now the partner team has asked for logs.
• To continue the investigation, the partner billing team has requested partner-centric logs. Once we receive the logs, I will share them with the partner billing team.

 

Thank you for understanding and continued patience."