As far as I know it is necessary to have at least $50 to withdrew money. If you want to give up of those $13 do not leave them like that. Go to the casino and chose casino Hold'em and have some fun for "your money".
I am a new poker player and there I made $32 of the $5 that I got from them. The minimum bet is $1, with no ante, and you only play against the dealer. He must have a stronger hand than 44 or otherwise he lose. Totally interesting and fun game if you know what you're doing, I think that you can make $50 and then asks them for your money and wait 4 months. It's your money, why would you have given them, they just want you to do so. Just imagine how many players also left at $2, $5, $27 etc, don't do that, please.
I would write to them every day and ask when I will get "my money". They're going to lose customers this way, I heard that many complain for withdrawing funds.