It was said to withdraw wihin 48 hours when I join, but it requires 30% of total amount to withdraw when I want quit and change a platform

At the beginning, it was telemarketing information about the booming stock market. Later, I said that the Taiwan stock market was not good. I hoped to join the trading platform to make a lot of profits. [And said that "If" there is leadier can led a group to make money, you need to pay 25% of the "Profit" as a commission. 】At the moment, I also agree and it doesn’t matter if there is a profit, but the amount of my deposit is only 15,000 US dollars so people don’t care me at all, I can only trade by myself. Because I don’t understand the software platform, I added the customer service to ask about the details of the deposit and withdrawal [Customer service indicated that the withdrawal only takes 48 hours to arrive in the account] After a few days of depositing 1000 USD, I try to withdraw 200 USD, After making sure that I can withdraw, I made a big investment of 15,000 US dollars and made more than 4,000 US dollars profit in my own operations. Since the New Year is almost here and I have friends on another trading platform, so I want to change to another platform and withdraw a big amount of fund, but I waited for several days. None of them are accounted for. I ask the platform customer service, the platform customer service said that the platform has allocated funds, and if the account is not received, you need to ask the president of booming stock via Line. I asked the president of booming stock, the president said that it was right that he stucked the money, and he unified the withdrawal on December 15th, and told me to contact his assistant at that time. On the same day, I contacted the assistant and said: If you don't let me withdraw the funds, you should push the numbers back to MT4. The assistant agreed. In the following days, the assistant kept pushing information about buying and closing positions. I think there will be problems later, so I didn’t copy the order. On December 15th, I want to withdraw. The assistant said that I need to pay 30% of the withdrawal amount as a channel fee before I can withdraw the gold. Hearing this, I am a little dizzy. Is this a scam?