Some F fares are non-refundable, promotional fares. Less than the P fare, sometimes even less than a Y fare. Do not assume that just because it is an F fare that it is refundable. READ THE RULES!! ALL OF THEM!!
If it is refundable, the refund method depends on how you paid for the ticket to begin with. Credit card purchases are refunded to the same card that was used to make the purchase.