A phone thought

Today I received invitations to get free 7 days in France! The day before this was for Turkey. All looks decent and cool. Is is not too good to be true?
Should I believe it as true and honest when it came from unknown source? What would you do?

And than, when you are asked to claim you free holiday package, they say pay us £20 admin fee but we will refund it later or something. The payment is via credit card. Would you trust this?

I don't, but I need to admit it is very tempting. Maybe you have this sort of experience which you would like to share? Or maybe I'm completely wrong and this IS honest and first class offer for a small price - a survey?

What do you think?