The email that your itunes/google play (or whatever you used to buy the gralats) is connected to will get a receipt after any purchase, find it and attach it to your ticket like they asked, and they should fix it for you.

Since we are already on this topic, if you get really unlucky you somehow won't get a receipt, even if money is removed from your acc. This has happened to me twice before, wasting $10 each time with nothing I could do about it