Thanks for your reply. I have already checked the law related to getting full refund within the 24-hour refund window. The agent over the phone told me that the reason why I could not get the refund was that I did not make the refund request within 24 hours. As per law, it is the cancellation time that matters. I don't know if I can use that point to get any attention from US airways.

Even if it really is a violation of the law, they will probably use the point that I can use the remaining value of this cancelled ticket to make another purchase. So basically, it serves as an US airways voucher now.