I am creating an online education portal for a client who pays on time and likes the work which I'm doing but after a day he says "Hey, I liked the work you did to the ABC section but after discussing with my partner/adviser I realized that without XYZ, ABC would not look nice and much functional."
Let me explain one situation: The website has a forum. The full layout of the forum was discussed and approved with the client before the starting of the project. Now when it has been created, he says to add a star-rating system in every comment. Now I have to create another module for this which will consume extra time and effort without money as this is a fixed-cost project.
So how do I deal with this type of clients such that they are satisfied as well as I get paid well?