Hello,
You should be able to go to https://account.microsoft.com/ and then go to Subscriptions, then look for something that says "Request a refund" and click that and request a refund.
If you don't see that, you can also go to https://support.xbox.com/help/subscriptions-billing/manage-subscriptions/digital-goods-subscriptions-refund and request a refund using the form that way.
Hope this helps.