[Buyer demanding extra work than the given instruction without increasing the budget]

Thank you everyone!

[Buyer demanding extra work than the given instruction without increasing the budget]

Hi,
I am recently working with a client who joined Fiverr in 2017 but has no review/rating on his profile. He gave me an article to write. I have written each and everything according to his provided instruction and discussed all the points given in outline. But now when I have delivered, he is demanding extra work (worth equal to the placed order) without increasing the budget.
I need your suggestion in this regard. How should I proceed with this client and task.
Thank you!