I can't withdraw my money from this platform.

I deposited 700 dollars now, then I received a call and they told me that I had to invest 4000 dollars, which I am not going to deposit since there is balance in my account, all I need is to withdraw what I've invested at least. Time passed and I did not have any response, after this, I requested the total cancellation of my account on this platform and they continue to call me to deposit more money that I don't have to complete some processes on the platform and I did not have any answers either. I don't get any answer. I send them emails, and ask them to call me but I don't have any response. Deposits were made through these means.