You should tell them that you have bought (ammount of money) gcoins with paysafecard/paypal/... , but you didn't recive gcoins to your account.
P.S to 1: Do not overdo it, I mean, don't say that you bought like 10k gcoins but around 150.
1b Include your username and password as a proof. You should also include your name (The one the account use).
1c As a proof you'll need to add some evidence. So, if you'll go with paysafecard then tell that you used that number: 8342-1993-1238-4330, if you got with paysafe card then just add your email instead of number.
2. Now, you'll probably get these gcoins. If you won't get EMAIL back or atleast private message on your account then try sending again or contact me here: firstname.lastname@example.org. I will reply and try to help you as hard as I'll be able to.
NOTICE: please don't use this for email recovery, the whole thing is meant for such issues.