Check the policy and the date
See whether the request is inside your refund window.
Say yes or no up front
Put the answer in the first lines.
Explain the reason if no
Be kind and offer transfer, credit or a donation instead.
Say how the refund is paid
State the method and expected timing.
Offer a transfer
Let them pass the ticket to someone else if you allow it.
Close the loop
Confirm when the refund is issued.