Hello
I saw you used the MacOS tag for your question.
If your free trial is via Microsoft website directly, you can use the AI Answer above. Cancel first, then contact support. I will give you more specific steps to contact support:
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, if it is from MacOS App Store, you need to request it from Apple, not Microsoft, because the payment processed via Apple.
Microsoft explains it here:
Apple's refund request instruction is here: https://support.apple.com/118223