Microsoft 365 features that help users manage their subscriptions, account settings, and billing information.
Sorry to hear about your father.
However, I'm afraid that we would not be able to help here as this is an open forum. What I would like to recommend here is to start an online chat via https://support.microsoft.com and click on Contact Us. Follow the instructions on screen until you get to a person (you could try selecting the option for more help). Once there explain the issue and they should be able to help you.
You'll more than likely need to provide proof of relationship with the parent account to support before they can help.