Refund still an option for those who forgot to refund (instructions in the post)
https://support.github.com/contact-next/product-selection/copilot/copilot-billing?source=default
It will ask you if you want a refund, agree, chat along. When confirmed, check: https://github.com/account/billing/history
You should see a refund record at the top.
That USD 39 is better spent on a homeless person.