I`m sorry to hear about the bad experience you had with your client.
I can't advise you what steps/actions to take but I would like to clarify the refund request. You have 7 days to respond to the request, If you don't respond in 7 days the funds will be released to your client. If you approve the request the funds will be also released back to your client. If you reject it, a dispute will be opened for you and your client. To learn more about disputes, you can check out this Thread. Thank you.