Greetings!
This is Tin, I understand that you would like to request a refund for your Windows 11. Kindly go to Microsoft Account Order History page and sign in with the account used to buy the Product and check if you will see a request a refund button there. If none, you need to reach MS Accounts & Billing to check on this:
Kindly open this link: https://support.microsoft.com/contactus/
Ensure that your MS Account has been signed in
Type "Chat with an agent" and hit Enter.
Please click the "Contact support"
Please select the "Products and services"
Please follow the prompts to connect with a live agent.
You may also choose the "Call me back" option if you prefer to receive a call.
Once you're connected to the Live Agent, please let them know about your issue so they could check your account and address your concern.
Thank you,
Christine