Microsoft 365 features that help users manage their subscriptions, account settings, and billing information.
To get help, open the "Get Help" app on your computer (just search for it in the Start menu). or go to https://support.microsoft.com/contactus, Type "Billing" and press Enter. On the next screen, click "Contact support" at the bottom of the page, then choose "Microsoft 365" > "Manage my subscription". You’ll then see the option to chat with a Microsoft support agent who has access to your account to help review the issue.
However, I do want to point out,
If you cannot locate the charges on your Microsoft account at all, it's possible that your credit card has been compromised. This means unauthorized charges may have been made on someone else's Microsoft account using your credit card. In such a scenario, you should contact your credit card company to open a dispute case. Microsoft is unable to directly investigate issues related to someone else's account if you contact their Billing Support directly. However, once a dispute case is initiated by your credit card company, Microsoft can then respond specifically to those claims through the dispute process with the credit card company. This is the appropriate channel to resolve such issues, as it ensures proper verification and handling of the unauthorized charges.