I have lost my 500 us dollars investment

I made an investment of 500 us dollars to this company and I was told that I was going to make a 3500 us dollars in seven days time . Then on the seventh day I will be expected to withdraw my investment. When that day came I could not make a withdrawal only to be told by the agent that my investment had profited more than it it should have . He further said that I was therefore expected to made a deposit of R8000 so that I can secure a software that will enable me to withdraw my investment.