Digital licenses, such as Windows 11, are generally nonrefundable. However, since this was an accidental purchase, your best option is to contact Microsoft Support directly and explain your situation. They may make an exception in your case.
Click this link: https://support.microsoft.com/contactus/
Sign in to your Microsoft account.
Select Windows > Click 'Get home support'.
Type "Chat with an agent" from the text field and press Enter.
Click "Contact support" at the bottom.
Select the product you need help with.
Follow the prompts to connect with a live agent or request a call back.