Client variable job demand

[muqaddastariq]

What if client's job description and verbally explained requirement are totally different and you have already done and submitted work (twice) according to written description. But now when I called and talked he need a totally different thing which is not mentioned in description. 
What to do now. Already half payment is funded in escrow (as first milestone) but not received yet. 

[sjbercot]

If you've done the work as he described in writing for the first milestone, the client can release it to you and fund a second milestone for the additional work with new requirements. Clients are not allowed to ask for free work.

[prestonhunter]

Muqaddas:
If you have a fixed-price contract, then the deliverable or task is described beforehand.

It can not be changed.

If a client hires you to draw a picture of a baby with 8 hairs on his head, and you do so, then the client needs to pay you. The client can not ask you to add a 9th hair. Such a request is out of line.

If a client asks you draw a 9th hair on the baby's head, tell him:

"Francis: That sounds like a great addition to the project. The original agreed upon task has already been completed. If you would like me to add that, you can close the contract and set up a new hourly contract to pay for the new work. Or you can add a new $50 milestone to the current contract. Or you can close the current contract and set up a new fixed-price contract for $50 to pay for that new work. Please choose whichever works best for you, and then I will do that new work."