Safricashop.shop, I want my money back

I have joined this company, to do online work which they eventually increases the price of the product I was purchasing, I have deposited almost 17000 to them which I couldn't complete the last task with them 2hich it wanted me to deposit 28800 which I told them I don't have such an amount, I can't afford to pay or deposit the amount they want me to deposit, I told them I want my money back I can't continue, now they are refusing with my money the are telling me I must complete the task which I can't afford the amount the want from me