Can i sue fiverr the company?

fiverr.com is a webiste for anyone who wants to sell anything or buy almost like eBay. I paid someone $400 to make me a iPhone app. The app was not finished and i opened a case and got only $350 back because fiver took the rest as a processing fee. Then i found out i cannot withdraw the $350 until i pay a $5.00 selling fee. Because i have never ever sold anything fiver wants me to pay $5 because that will activate my selling abilities and then my selling abilities will unlock a button called REVENUES. WHICH WILL THEN send my $350 into my revenues where it will then be allowed to returned into my paypal account. But before its returned they want to charge me another processing fee because they will then believe i sold something for $350. They told me my best option is to use this $350 as a credit on the website to buy other things. I DONT WANNA BUY ANYTHING OFF IT ANYMORE I JUST WANT MY MONEY BACK ITS BAD ENOUGH IM ONLY GETTING $350 out of $400 back and now they wanna mess with me even more and charge me more random fees. I need legal help what can i do? Its been 4 months now and i still don't got my $350:( iv been so stressed and depressed and ANGRY! I need legal help how much would it cost to sue them? How much can i sue them for? FORGET THE $350 i want MORE THEN THAT NOW FOR THIS BIG HEADACHE THEY HAVE CAUSED ME! Is it worth a lawsuit or I'm wasting my time? I looked up their company its worth over 5 million

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