Client: "I need you to implement a feature which does x"
Me: "We can it do like this, I can do it in Y hours."
Client: "Perfect do it"

Me: "Here you go have a look and if you give your ok I'll implement it on production."
Client:"That is not what I need. I need Z"
Me: "Well then you should have said Z and not x. But I can do Z if you want me to."
Client:"Do it it is urgent!!!!111"

Me: "All done here you go."
Client: "That works like what I said what I need, but I meant more like xZ."
Me: "Ok, you know I have to charge you for all this, do you?"
Client: "What why? It isn't the feature I wanted!!11 Do it right and I'll pay you for the right one!"

Me: "It might not be what you wanted but it is exactly what you specified to me. I'll send you the bill and will not continue working for you. Good luck finding someone who is willing to do unpaid work for you."

I am so done with that kind of client.