I may be more qualified then, I work in fraud. I accidentally called a fake airline number to get a refund for a Delta ticket and happily gave the guy my credit card for some such fee. If requiring a credit card fee to get a refund isn't a red flag, I don't know a better one. To be fair, my sister had found the number and three way joined me in because I was helping her buy the ticket. So an extra rule: don't even trust a phone number someone you know found because /they/ might have been the first victim and passing compromised information to you.