Hello Lok,
Thank you for posting question on Microsoft Windows Forum!
Based on your query of receiving a direct debit without a recognizable invoice or subscription. Well! This forum is just a user to user forum, no-one here has any account access. In fact, Microsoft has a process for handling billing disputes and refunds, but it requires going through their official support channels since only they can access your account and payment records.
For more information about refund https://support.microsoft.com/en-us/account-billing/how-to-get-a-refund-on-a-microsoft-subscription-67dca30b-b323-44d5-acc2-e02f9902c472
Please note: Keep screenshots of your account charges, credits shown, and bank statements. This will make your case clearer when speaking with support.
For further reference regarding billing and subscription, please consult the following articles.
Hope the provided information is helpful! If it is. It is appreciated to consider clicking "Accept Answer".