Inducing clients to participate activities and unable to withdraw

This forex trading platform induced to participate activities. I deposited money and earn a small profit. It was said that it can be withdrawn after event ends, but they were saying that it requires to pay 20% tax and it cannot be deducted from platform. It has to be paid separately. I had deposited all the cash, there is no more for paying tax. I contacted customer service, but they ignored me and not answering my question. I am seeking for help now.