Please report it hear if you have evidence. If you don't, then I'm afraid you wont receive a refund. :/
http://www.skyblock.net/forums/server-reports.328/

if having a witness is evidence i do

Unfortunately, that doesn't count. We only accept full screenshots and videos.

crap ugh but what is a rare key?

It's a key you use to open a rare crate at "/warp crates" to get rewards.

how dod u get one because i got scammed out of a diamond the guy said it was a rare key and then scammed me and left