The buyer gives me his requirements and as usually I am done my work and before delivery, I gave him to show the works. But now he gives me another requirement and tells he has needed to work this requirement.
Ask your buyer to place an order/purchase an extra if he has a new project or new requirements for the same project. If you’ve completed the work he paid for according to the instructions, you should’t be forced to do additional work that wasn’t within the scope of the order and wasn’t paid for.
but he will do not pay for this order
You can either do what he asks or refuse and ask for payment if you’re sure you’re right. You could also try asking CS for advice, but they’ll probably want you to try to work things out with your buyer on your own.
I would also think twice before working with this person again.
Thanks for your advice