Hi, thank you for reaching out to the Microsoft Q&A forum. I’m happy to help.
As far as I know, digital purchases like a Windows 11 license are not refundable. However, since this was accidental, I suggest contacting Microsoft Billing Support directly and explaining your situation. They might consider making an exception.
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.
Customer service phone numbers: https://support.microsoft.com/topic/customer-service-phone-numbers-c0389ade-5640-e588-8b0e-28de8afeb3f2
To access the full range of support options, including chat, please contact them during business hours which are Monday to Friday from 9 AM to 5 PM local time.