Hello, good day and thanks for your question. I understand that you are checking with regards to refunding the Windows 11 that you have purchased.
If you changed or updated the product key using the ones that the university has provided you then it has upgraded it to Windows 11 Education.
If you have purchased it from Microsoft, you may check if you will be able to request a refund when you login at https://account.microsoft.com/billing/orders.
In the event that the refund option is not available from there, you can reach out to the support team at https://support.microsoft.com/en-us/contactus/ and then click on Windows and then click Get Home Support and then type in Refund request and click the blue button that says Sign in to contact Support and login and proceed from there.