H1B filing fee - Refund issue with Employer


I applied H1B for FY 2015 through a consultant employer and my petition was not selected in lottery. My employer took 2.5K dollars from me and he is not returning the amount back to me. Whenever I asked, they are delaying by promising that they will send in a every week, this happens for past 2 months. Is there any possible way to handle this or I need sue them through an attorney. Please suggest.